Harry Fenton's Hints and Tips for Small Continental Engines

Updated 26 July 2012

Harry Fenton is an A&P and has owned numerous airplanes over the years.  He's been providing a lot of good advice on maintaining Continental engines to the Fly Baby mailing list.  With his permission, I've begun archiving the information he's provided into this web page.

If you have a question, you can email Harry directly.  Note:  This "mailto" link is deliberately messed up to prevent automated process from grabbing Harry's address and flooding him with spam.  After you click the link, type in his first name in front of the "@" symbol.  In other words, his address is:

When you write Harry, do him a favor and give as much information about the airplane and engine as you can...total time, prop info, etc.  Note that Harry will respond with a personal email.He cc’s me on the messages, and I update this web page on occasion.  Realize that your email exchange with him will probably end up on this page to help others, but I make every effort to delete personal information such as names, phone numbers, email addresses, and even aircraft types, in some cases.


Please note that Harry answers questions from people with a wide range of engine-maintenance experience, from absolute tyros to A&Ps with Inspection Authorization.   As such, Harry's advice sometimes covers some pretty complex procedures, procedures that tyros really shouldn't tackle.  The instructions provided are informational and not necessarily the absolute step-by-step process to the do the job. 


It is assumed that the person conducting the maintenance meets the FAA requirements for training or field experience and is appropriately rated.  To quote Harry, "Should something go wrong, the responsibility of the “smoking screwdriver” is yours, not mine."



Text in italics are quotes from other folks' emails...they aren't Harry's words.

If you're looking for general information on engine options for Fly Babies, see the main page.

I have attempted to categorize these as best I can, but many fall into new areas or across areas.  If you, at first, don't see the subject area listed, do a "find" with your browser to search for key words.  Keep in mind that information may be split between categories.  If the first article doesn't address your issue, keep searching....many times, the same issues come up more than once.

Keep in mind, too, that there is a LOT of commonality in operation between the Continental models.  Just because the title is "O-300 Missing" doesn't mean you won't find something that'll help on your A65....

Subject Areas:


For those with Continental O-200 engines, Harry recommends the engines section on the Cessna 150 Web Page.

Issues with Other Engines

While this page is aimed at those using the small Continentals, Harry occasionally fields questions about other engines.  Here are the links....

Starters and Small Continental Engines

The A-65-9 is the only A-65 configured to accept a starter and very few were made.  As such, certain unique parts are very difficult to find and parts for the Eclipse starter are as scarce as dinosaur DNA.  The -9 accessory case is unique and different than later -12, -14 cases equipped with starters, but relatively available because most -9 engines were converted to -8 configuration.  The C-75-12 through the O-200 use the same accessory case and engine accessories and may more parts are available to support these engines.  A major headache with the -9 is magnetos as the only type approved are the very heavy (8lbs each!) Bendix SF4 non-impulse magnetos.  There are no Slick magnetos approved to fit the -9 engine.  By the time all is said and done with the weight of the -9, it is marginally lighter than a C-85-12 with lightened modern accessories.
The most practical choices for small Continentals with starters are the C-85-12 or O-200.  Lightweight alternators, starters ad magnetos are available that can shave 12-16 lbs off of the dry weight of the engine.  The C-85 uses a slightly lighter case than the O-200 and is even lighter yet.  If you want to get fancy, there are various vacuum pump drive gears and bosses on the case that can be shaved off for a couple of pounds of weight savings.

Price wise, the C-85, O-200 series are very competitive with the A-65.  A running, but high time O-200 can be had for $2000-$2500, or for $1500-$1700
for an accessory bare core, and all parts are available new.  The A-65 is a good engine, but tapered cranks tend to be cracked at the keyway, the magnesium accessory cases tend to rot, the oil pump pockets go bad, and finding good cylinders can be a problem.  Don't get me wrong, the A-65 is a really fine engine and continues to be a bargain, but the O-200 is kind of a sleeper that can still be bought and overhauled for not too much more than an A-65.

On the plus side of hand propping the A-65, the availability of dual impulse magnetos vastly improve the starting characteristics.  Another starting idea to consider is the old lever and cam starter that was used on Aeronca Chiefs.  Basically, the pilot pulled a lever  in the cockpit which pulled a cable connected to a latching mechanism on the crank- pretty much identical in working concept to a rope pull on a Briggs and Stratton engine. Unfortunately, these starters are nearly impossible to find, but the concept may be duplicated with some work.  I think that the National Aeronca Association may have access to drawings for the pull starter.

Sky Tech has introduced an O-200 starter that is a direct fit for the pull start or key start and just bolts on, which is a more simplified installation than the B&C.  The B&C requires that the clutch shaft be removed in the rear case of the engine which involves engine disassembly or accessory case removal to saw off the shaft.  The pull start doesn't use a clutch, so no problem.  The stock pull starts are still relatively cheap to overhaul, which is a positive.

Another possibility on the A-65 would be to fit a starter to install in one magneto hole, an alternator to fit in the other and use a Light Speed engineering electronic ignition triggered from the crank.  The beauty part of homebuilding is that the options are unlimited!

March 2002


Pull-Cable Starter Maintenance

Hmmm... do the pull-cable starters tend to develop problems, too?  I've noticed lately that my starter sometimes doesn't seem to have enough oommmphhhfff to pull the engine past the compression stroke.  It stops and whines.  I back off on the cable, and when I repull it seems to get past that first compression stroke and kicks it around fairly well (it starts fast, so there's no real issue).
Sounds like a B&C starter might be in my future, but I'd have to hang a new button for it, add a solenoid, etc.

The pull start is the most reliable of Continental starters, but your problem is common.  The solenoid and clutch on this starter are actuated by a pull cable and lever arrangement.  When the cable is pulled, the arm pushes down on a contactor for the motor and pushes the clutch forward to engage the starter.  Over time the cable stretches and adjustment may be required.  On the arm is a threaded rod and locknut and the engagement action can be improved by adjusting this.  However, be careful, as there is a relationship between the position of the arm and the engagement of the clutch- I think that it is possible to overadjust and have the clutch not engage properly.

Another possibility is that the contactors are dirty or worn.  There is a triangular piece on the starter where the pull cable arm contacts the plunger.  If you remove this piece you will see a couple of copper blocks. Squirt some carb cleaner or contact cleaner in between the blocks to clean the surfaces.  These blocks are no longer available, but I think that you can break a snap ring that holds the top one in place and literally turn the contactor 180 degrees- it will probably work fine for another 50 years.

If you decide to go with a new starter, use the Sky Tec.  It bolts on your engine with no mods and has a built in solenoid.  All you need to add is a push button switch or key switch.  The B&C is top notch, but requires engine mods, is pricey and overkill for the mission profile of the Fly Baby (cheap flying).  The B&C is perfect for the high start cycle environment of a flight school.

(In addition to Harry's writeup here, I've incorporated some of Harry's comment and my own experiences on a special Continental Pull-Cable Starter Clutch page.)


Saving Weight on an Electrical System, and Some Handpropping Advice

The O-200 with a lightweight starter and no alternator is a great option. You can get about 8-10 starts from a battery and just top it off with a trickle charge each night.  I did this on a VW powered Sonerai II that I owned and it worked great.  I hooked up an external receptacle to plug in the charger and popped a cord in after each flight.  I even got fancy with a later iteration and moved the battery externally and used an APU plug on the fuselage.  I would crank up, pull the plug and go flying.  The only negative was if I visited another airport, and then I had to hand prop.
[RJW Note:  If you don't include an alternator, you do not have to have a transponder to enter the "Veil" around Class B airspace.  You still can't enter either Class B or Class C, but you can fly to airports under the Class B without a transponder.]

I have gone back and forth on handpropping and starters on several airplanes.  As always, there are pros and cons, with no clear solution.  My preference is a starter, but if I hand prop I always  tie the tail down and chock the wheels, or get someone to hold the tail while I prop, or have a qualified person prop the engine.  Another key is to always use the same starting technique- this minimizes the risk of forgetting where the throttle is, switch positions, etc.  Typical start on the A-65 or O-200 was 2-4 shots of prime for the first start of the day, switch off, pull the prop through four times to get fuel in each cylinder, switch on, swing and start.  If the engine floods, turn off the switch, full throttle, pull the prop backwards 8 blades, pull the throttle back to idle,  check the throttle back to idle again and speak out loud, "throttle closed", leave the switch closed, pull the prop through two blades, check the throttle, switch on, crank.

Consistency is key.  And yes, I have been run over while handpropping, hence the careful technique.

March 2002


Stromberg Carburetor Mixture Controls, and some Alternate Carburetors

On the Strombergs used on the A-65 through C-85 there is a mixture control that is wired closed.  I have flown a C-140 with the mixture  hooked up and it seemed to have zero effect on leaning.  This valve is wired closed on virtually every single Stromberg I have ever seen, which is probably a testament to it's usefulness.  The only time the mixture might need to be fussed with is at very high altitude airports, but even then I don't think that the mixture control has much authority.
Regarding carbs, I have used the Ellison on an A-65 engine with good results.  The lean control on the Ellison is finicky and non-linear, meaning that if you have 3" of control through nearly all of the leaning action occurs in the last 1/2" and is difficult to dial in, requiring the use of  a vernier control.  Ellison is very helpful and suggested that different metering needles may help the condition.  I never did get around to sorting out the metering, so I just wired the mixture full rich.

A friend with one of the new Aero-Carbs is experiencing the same issue with leaning.  The Aero Carb, though is very reasonably priced at $350 and seems to work reasonably well.

March 2002

[RJW Note, October 2004:  I have a Stromberg and haven't found much use for the mixture control.  But I got email from Ed Burkhead, who says, "The mixture on the Stromberg works accurately over the full range - but it works slowly...After getting level and stable in cruise, I found myself pulling VERY slowly on the mixture control or pulling and waiting a bit.  With my large-scale EGT gauge, I found I could control the EGT to 10 degree accuracy. I used 50 degrees rich of peak for cruise and 100 degrees rich of peak for high power (long climbs or high altitude takeoff)."

Ed suggests disassembly of the carb and cleaning of the tubes that provide the air flow and vacuum for the mixture control.]


Undersize and Oversize Pistons and Cylinders

[The original questioner here had a variety of cylinders to build up his engine with...of a collection of 11 cylinders one was "yellow tagged" oversize, one was standard which appeared like new, and four badly worn and tapered standards.  The others were .002" to .005" beyond oversize service limits, but with good clean round bores.  He asked for Harry's advice on the best route to take.]
Mixing undersize and oversize pistons and cylinders does not pose any operational problems.  The only real problem comes when replacing cylinders down the road and making sure that a standard piston does not get installed in an oversize jug.  I just helped fix an engine where this very event occurred.  Somebody had installed a .015 over cylinder onto the only standard piston out of the four on the engine.

Ironically, you can buy .015 pistons cheaper than standard- $60 vs $68. Chroming is an option to bring the cylinder back to standard bore, but part of the chroming process involves overboring the cylinder .020-.030 anyway. I usually go to .015 and drop in new pistons before I chrome.  It is usually six of one, half a dozen of the other in terms of rebuilding existing cylinders vs swapping for overhaul exchange. Superior offers really nice new cylinders, but the cost for a set is nearly 3 grand- kind of overkill for our little wooden birds.

[A follow-up message by Harry]

I'm sitting here thinking about your cylinders and your best option will probably be to go with chrome barrels.  When a barrel is chromed it is bored way oversize (something like .025-.030) and the chrome is used to return the barrel to standard dimensions.  Cylinders with bad bores are prefect candidates for the chrome process.  If all the cylinders are standard then one set of rings can be used, pistons etc., and everything is matched.  A benefit of chrome is it is very resistant to rust.  There are some problems with breaking in chrome, but these problems are usually associated with high horsepower engines.  If you have one .015 over cylinder, I would keep it on the shelf for a spare and go with a matched set of cylinders.  I'm spending your money, but a little up front will often save a bunch in the long run.

Make sure that you inspect used parts very carefully, especially the pistons.  Once again the condition of the ring lands and gaps are crucial. I've built a number of "mongrel" motors from scavenged parts that have worked reasonably well, but the biggest problems arose from used pistons and used rod bolts.  Yes- A-65's can throw rods!  I have some personal experience with this...

March 2002


On Carb Heat

[On this message, Harry was responding to a Fly Baby accident where the aircraft allegedly climbed too slowly after taking off with carb heat on.]
The NTSB report does not provide any indication of ambient temps from which to figure density altitude, but a base altitude of nearly 4000 feet MSL is pretty high.  Next time you are out flying, level off at 4000 feet idle the engine back to 1700-1800 rpm and pull the carb heat on to note the effect on rpm drop.  I'd wager that the engine will drop significantly in RPM.

One of the effects that heating the induction air charge has is to effectively enrichen the mixture.  The heated, expanded air will have many fewer oxygen molecules per fuel molecules, and, bada-bing, richer mixture. I have seen this type of accident many times, and a characteristic clue is that the plugs are very black, with a sooty to hard carbon look, kind of like black anodizing.  Leaky primers and no mixture control on the carb really aggravate this situation.

Lots of factors can play into this type of accident such as general engine condition, recent operation of the engine, even recent pilot flight experience. Given the relative high altitude of the accident airport, the effect of the prolonged use of carb heat would have been more significant, and quite likely did result in reduced engine output.  the final NTSB report will likely cite the pilot's failure to maintain airspeed and improper use of engine controls which resulted in diminished engine output.  Touch and go's are particularly susceptible to this type of accident because the pilot may be short of runway, with lots of distractions while trying to maintain control to go around.  Even a Fly Baby cockpit can get busy under the right circumstances.

Regarding carb heat use with Continentals, I have had more icing experiences with C-85 and O-200 engines than any other type!  The Midwest has a lot of dewy mornings that are perfect for flying, but perfect for developing carb ice.  I get involved with a number of post accident investigations and carb ice is a leading supposed cause for many engine failures where no hard mechanical failure or pilot mistake can be determined.  Establishing the dewpoint at the time of the accident is usually number three on the list after determining if fuel was on board and selected or if there was an obvious mechanical problem.

April 2002


A-65 Rebuild - Cylinder Studs

As long as your engine is apart let me offer a couple of suggestions.  Be sure to carefully inspect the fit of the fixed studs in the case halves.  A very common problem is that the male threads of the steel studs tend to pull through the female aluminum threads in the case when the cylinder hold down nuts are torqued.  Once the threads strip and the stud is pulled, the only way to fix it is to disassemble the engine.
Sooo....on the engines that I overhaul, I automatically pull out the studs and install helicoil inserts to prevent studs from being pulled when cylinders are installed or changed in the field.  Once again, there is some cost and hassle up front, but a small price to pay when a stud is pulled during a cylinder change.  On an A-65 the stud issue is not as critical, but on an O-200 used for commercial operations, it is essential as cylinders are like to be changed frequently over 1800 hours, thereby increasing the risk of a stud pulling.

Regarding oil pump gears, the single biggest post overhaul problem with an A-65 usually involves oil pressure.  Measure the oil pump pockets for taper and concentricity.  The oil pressure is completely dependent upon the very close edge tolerance of the oil pump impeller gears vs the diameter of the pump housing in the case, so even a small amount of leakage will result in low or no oil pressure.  This problem is frequently misdiagnosed as a weak oil pressure relief spring and I have seen all sorts of fixes  increase pressure of the  bypass spring to get oil pressure in the right range.

The oil pump well should be free of scoring, also.  Some very light marks are ok, but anything that you can see or feel with a fingernail is no good. Unfortunately, the -8 accessory case is made of magnesium, so traditional weld repairs are not possible.  I have had some success overboring and re-bushing the oil pump pocket, but call me before you do this.

I would also just buy a new oil pump cover plate.  Leakage across the surface where the gears ride also results in low or no oil pressure.  Also, torque the cover plate evenly as it is thin and can warp, which will result in low oil pressure.  Don't use any sealants on the cover

A final accessory case issue:  the oil pressure relief valve plunger and mating surface in the case cannot be scored.  Once again, I automatically buy new oil pressure relief valve plungers and springs at every overhaul. If the existing plunger looks good, fit a dowel in one end, apply a minuscule amount of  valve lapping compound to the face of the plunger and lightly lap the valve into the mating surface in the case.  After lapping, flush the heck out of the case to remove all traces of the lapping compound.

Preparation up front usually results in good oil pressure, but be prepared to pull the accessory case off a couple of times to get oil pressure tweaked in.

April 2002


A-65 Rebuild:  Lifter Plunger

The hydraulic plunger assembly that inserts into the lifter body should be checked for leak down prior to installing into the engine.  The plunger is a spring loaded device with a internal ball check valve that is pressurized with engine oil and takes up the lash in the valve train.  A common problem here is that the plunger can go "flat" and not pressurize which results in insufficient lift to open the valve, resulting in a cylinder dropping off line.   The good news is that plunger valves usually don't fail, but can get gummed up and stock over time.
I don't have the exact specs at my finger tips, but they can be found in the A-65 and O-200 manual. The test is simple:  drop the plunger assembly into clean Stoddard solvent and pump the assembly with your fingertips until it is pressurized.  The plunger should hold the same relative pressure for a period of time (five minutes, I think, but look it up in the manual).  If it leaks too fast, then replace the plunger.  Once again, check this ahead of time as the entire cylinder assembly needs to be pulled to get to the plunger valve.

April 2002


Buying an A-65 With No Logs

I usually don't worry too much about lack of logbook information as the "current state condition" is really what counts.  As long as compression is in limits, oil temps, pressure, and consumption are in line, you should be good to go.
The A-65 crankcase is aluminum and light surface corrosion is not unusual. You can scotchbrite the corrosion with no problems.  don't use steel wool as the little steel wool fibers can imbed into the aluminum and set up intergranular corrosion.

Oil leaking between the sump flange and the case is a chronic problem.  The case halves, the accessory case, and the sump surfaces all of junctures at the that point on the engine, so sealing it is a chore.  You will probably be unsuccessful if you try to goop on gasket sealer externally, but it is the first easy fix.  You will probably find a equally non-productive results by retorqing the sump nuts.  Squeezing the gasket more never seems to help.

A more permanent solution is to pull the sump and replace the gasket. Pulling the sump is not complicated, just tedious.  There is limited clearance of the nuts to the flare of the sump body so each nut is turned a couple of turns in a progressive manner.  Once the sump is off, clean the mating surfaces of the sump and case.  There will always be some steps in the case where the case halves and the accessory case meet, so don't worry about this too much.

Inspect the sump for cracks around the neck, a relatively common problem. The sump flange should be relatively flat.  A lot of times the holes in the sump flange through which the mounting studs pass become kind of countersunk after 50 years of overtightening to cure oil leaks and need to be smoothed a bit.  A flat surface like a kitchen counter top will suffice as a flat enough surface to find distortions in the flange.  There will be some unevenness, but don't sweat this as the replacement gasket is relatively thick and will absorb small distortions in the mating surfaces.

My current favorite method of gasket installation is to apply a thin film of permatex non-hardening gasket compound to the ID and OD of the gasket to seal the edges.  Replacement sump gaskets can be bought from Aircraft Spruce (p/n3577-@$1.08ea).  Next, apply a thin film to the sump flange and the case mounting surface.  Don't lay it on too thick as the excess permatex will squeeze out and the extruded excess can fall off of the flange and get into the oil supply.

Re-install the sump and torque to book specs.

The above technique works pretty well.  I prefer the non-hardening Permatex as it is easier to remove than he hardening type if you have to do any repairs in the future.

May 2002


Refurbishing a Sensenich Propeller

Be careful on stripping paint.  I just read in the Globe Swift tech notes about how some paint strippers have a more acidic content than others and even some paint strippers that are labeled as an "aircraft" stripper may be using the term for sales purposes as opposed to a description of it's true compatibility with aluminum.  My take on it is that most strippers are probably ok, but just flush the stripped surface with water and maybe a baking soda solution to stop the acidic action.
Torque values can be found at http://www.sensenich.com/misc/mpinstal.htm. Basically, 3/8" bolts are torqued to 23-25 ft/lbs and 7/16" bolts get 40-45 ft/lbs.  By the way, www.sensenich.com has lots of really useful info on props.  I think that Aircraft Spruce and Chief Aircraft sell the official gray paint used by Sensenich, also.

May 2002


Sticking Floats on Stromberg Carburetors

This is a chronic problem with the Stromberg carb on the A-65.  A new Delrin tipped valve and a new seat can fix this problem, but the valve and seat are pricey- I don't have the numbers in front of me, I recall about $200 or so, but I may be wrong.  Even the new valve an seat may leak a bit.  The float may have also wiggled out of adjustment through the years preventing the valve from fully seating.
Depending upon the severity of the leak, it may be something you just live with.  Your best gauge on how the engine is running is to look at the plugs for evidence of carbon fouling.  If you can, measure how much runs out.  If is just a tablespoon or so, it may not be a big worry.  If the float bowl and sump empty, then it needs to be fixed.

I'm not sure if you are planning to fix it yourself or send it out.  I never fix my own carbs and I always send them to the guys who are the experts  One of the best accessory shops that I know just happens to be in Rockford, Aircraft Systems 815-399-0225.  These guys do top notch work and are very supportive of antique parts.  A tad on the pricey side, but the best at what they do.

May 2002


Replacing the Front Seal on an A-65

This is one of my least favorite jobs!  The correct seal should be split with spring that snaps in around the center groove of the seal. It is easiest to install with the prop removed.  Be sure to mark the prop and flange so that you can re-install the prop in the correct orientation. Also, if you have a spinner installed, mark the relative position of the spinner, bulkheads and prop.  The non-split one piece seal is for tapered shafts.  The split seal is usually green or black in color and the non-split is typically red.
For tools, you will needs a pair of needle nose pliers with long skinny tines (grabber thingies? jaws?  What do you call the business end of a set of pliers?)  Also, a small awl with a 90 degree bent end will be needed.  A couple of boards thin enough to fit between the crank flange and case and long enough to provide leverage to seat the seal will also be used.

First remove the old seal.  The best way is to pierce the seal with an awl in the center of the seal face and collapse it down or cut a section out so that you can get some pliers on it.  Be careful not to scratch the shaft or gouge the case with a screwdriver.  After the seal is out, inspect the surface of the crank where the seal rides.  Excessive grooving on the crank can be a problem.  Lightly polish the area with emery cloth to kind of polish the small imperfections out.

Lube up the crank with motor oil- don't use silicone or lithium grease as the seal will never establish a firm seat and it will continue to leak. Install the seal with the concave end toward the engine and the flat side towards the prop flange.

Now the fun part!  Loop the spring around the crank and connect the ends. Using the awl and needle nose pliers, work the spring loop into the inner flange on the seal.  It will undoubtedly pop out several times as you try to do this.  Another method is to loop the spring into the seal flange, and pull on the spring slightly to keep it seated in the flange and hook the two halves together.  I've been able to do this and have the whole assemble pop together.  In any case, be patient as there is not much room to work and the small hooks on the end of the spring can be tough to get hooked just right. I usually keep extra springs in stock as it is not unusual to bugger them up during installation.

Once the spring is in place, lightly press the seal into place using a pieces of wood that is thin enough to fit behind the flange and long enough to provide a good bearing surface.  The key is to press evenly so that the seal seats evenly.  I usually do not press the seal fully flush with the case, but I leave it out 3/16" to 1/8" to as much as a 1/4".  This places the bearing portion of the seal on a part of the crank that is still standard size and your chances of keeping oil in are much higher.  If you fully seat the seal, it will ride in the most worn area of the crank and recurring leaks are more likely to occur.

Finally, once the seal is in place, take your thumbs and press against the center of the seal where it sets on the crank the get the bearing portion centered on the crank.  Typically, during installation, the bearing surface drags a bit and will remain just a hair convex towards the back of the crank flange.  By seating it with your thumbs, the seal will be correctly positioned.

June 2002


Prop Orientation During Installation

The key to prop orientation is to get the blade in the right position for hand propping.  First step is to identify blade number one on your prop. Usually, but not always, the prop is marked at the hub to denote blade one and blade two.  If I remember, your prop has this stamped an the forward face where "McCauley" is stamped.
Next, take the top spark plugs out of the engine.  Removing the plugs reduces the compression making the engine easier to turn and absolutely prevents the engine from starting.  I cannot stress enough that ignition switches cannot be trusted!!!!  Any time that you plane to work on the engine or turn the crank, pull the plugs or physically attach alligator leads to the p-lead stud of the magnetos to ground the mags to the airframe. I have had several engines start on me while I was moving the prop.  My favorite was the Navion on jacks that started at full throttle, but I digress.

Put a thumb over the spark plug hole on cylinder number one and turn the crank until you feel compression.  As you turn the crank to top dead center (TDC) the impulse couplings in your magnetos should snap at about TDC.  With the engine set at TDC, install the prop with blade #1 to the left as viewing from the nose back to the tail of the plane.  The prop should be mounted horizontal or slightly past horizontal on the down stroke of crank rotation, typically winding up with the blades in the 9 and 3 o'clock position- or thereabouts (I'm rattling this off from memory which may not jibe with reality).  Basically, all you are doing is setting the prop in the best orientation for hand propping.  You don't want the impulse couplings to snap to fire the engine with the prop vertical, for instance.  Some engines may use non-impulse coupled magnetos, but the set up procedure is the same- orient the engine to TDC and install the prop to give you the best position for hand propping.

A final note on prop orientation on certified aircraft.  Some certified planes, usually late model Pipers, install the props in a specific orientation that is not optimum for hand propping.  Usually the blades wind up at the 7 and 1 o'clock position to dampen out vibration.

June 2002


Modifying A-65 Engines to Accept O-200 cylinders

A list participant writes:
> I have a chance to pickup some decent o200 jugs and was wondering if a guy can bore the A65
> case and make the Cylinders and pistons  work with the A65 crank.  My research indicates that
> this should work with perhaps a custom piston pin bushing.  I would balance the
> engine and  operate at reasonable rpm's, say 2450 max 2200 cruise to keep torsion and vibration
> from twisting the smaller case.  I would use standard pistons and CR.  My purpose is to build a
> custom motor and utilize the engine I have to build a custom -8 configuration. I am an old
> hotrodder and Diesel mechanic by trade and would love to tackle this

[RJW Note - Harry has amended his answer since his original posting.   I have changed the following based on his comments.]

Although I've never done it, the A-65 case could probably be bored to accept the O-200 jugs.  The C-85/O-200 cylinders have a bigger bore than the A-65, the bolt pattern is the same.  The cylinder holes in the A-65 case would have to be opened up to accept larger bore cylinders, but that could be done with little trouble.

Next, the C-85 crank and rods will drop right in and is the same throw as the A-65 crank.  So with the C-85 jugs and C-85 crank, the A-65 could deliver basically C-85 performance.

The jury is still out on using O-200 lifters with the A-65 or C-85 cam, but I'm in the process of sorting this out.

However, before everyone runs out and starts hacking up their A-65, keep in mind that the C-85 case (until I'm proven wrong!) is a bit more robust.  My best recommendation is that if one has a mixture of A-65 and C-85 parts lying around, then it would be possible to build an engine.  However, I  still wouldn't recommend  purposely building a hybrid as there are plenty of C-85 or O-200 engines to be found that could accomplish the same end to the means in a more reliable manner.

As a point of interest, the Formula One air racers have used C-85 pistons in the O-200 for years for extra power.  The C-85 piston pin bore is a bit lower in the piston, so with the longer O-200 crank throw the net result is a bit more compression which yields 15-20 more hp.  Further to the Formula One mods, they are required to modify C-85-8 case with an extra case through stud and welded reinforcements to the case.  The O-200 case is much beefier, has larger diameter through studs and more of them.

The best way to hop up the A-65 is to balance the internal engine parts and drop in high compression NFS pistons manufactured by Lycon Rebuilding.  The pistons are expensive, but way less expensive and more reliable than extensive case mods.  In terms of RPM, the A-65 turns a measly 2300 rpm, so spinning up to 2500-2700 will yield more hp with the high compression pistons.

Be aware, though, that the A-65 connecting rods are much less robust than the C-85 and O-200 connecting rods, so I would not run much past 2700 rpm if you want to maintain reliability.  If you compare the A-65 and O-200 connecting rods you will see that the neck and crank end of the A-65 connecting rod is about 20% less beefy than the O-200.  Any cylinder and compression mods will be limited by the strength of the connecting rod.

Having said that, I have an A-65 built which is hopped up and should produce around 100-105 hp.  I beefed up the A-65 case by welding in some reinforcement plates around the cylinder base studs, welded a weak joint at the #3 bearing web, installed an extra through stud, re-indexed the cam to optimize the lift from 2300 rpm to provide more power at 2700 to 3000 rpm, ported and flowed the heads, installed 10.5:1 compression ratio pistons, align bored and dynamically balanced all of the reciprocating parts, and installed an Ellison throttle body.

I have not run this engine yet as the airplane it is destined for is still under construction, so I can't report if my work is best way to do things. If you simply drop in high compression pistons, balance the internals and run a couple hundred more rpm, you would probably achieve 90% of the same results and maintain an acceptable level of mechanical reliability.

August 2002


Welded Repairs to Engine Cases

A list participant asks:
>  Just some questions, hoping someone might be generous enough to answer. Is
> it considered normal practice to weld aircraft engine crankcases? Do the
> cases have to be stress relieved and/or remachined and is it generally
> considered a safe procedure?

It is very routine to weld crankcases and cylinder heads, however the specific welding process and the areas that can be repaired are defined by the FAA in the case of FAA approved components.  Of course, for experimentals, the rules are more open for repairs, the bottom line being that the person performing the repair needs to be sure of the airworthy nature of the repair.  Not all stressed areas are approved to be welded, but as far as I can tell, most companies involved in repairing crankcases are able to repair 90% of most damage.  On the small Continentals it is common for the #3 bearing web to crack and require welding.  In have had instances where he web literally fell out of the case and it was legally welded up with no problems.  About the only case repair not approved is if there is literally a hole in the case from a thrown rod.

As far as stress relieving goes, I can't really answer that, but I assume that the welded parts are heated in an oven for stress relief (I have seen ovens repair facilities and I assume that this is their use.)  I have simply sent cracked cases off to am shop and they come back repaired, so I haven't really seen the process start to finish.  I'll do some checking and post a follow-up answer.  Overall, welding is a safe practice as 70% of all Continental engine case have probably been welded and maybe 20% of Lycomings have had some kind of weld repair.

August 2002


A-65 Internals in a C-85 Case


> Harry, in an earlier post you suggested it was possible to use A65
> internals in a C85 case.  From your earlier post C85 rods would be
> appropriate with C85 cylinders and piston assemblies.  What else
> would be interchangeable with the A65 internals?  My A65 has the mags
> you put on, would the mags and gears work for a -8 C85 as well.  I am
> researching this as I've located a case and was wondering about the
> feasability of such a swap.  It seems the C85 cam is a different
> profile but what about lifters and using the A65 cam gear?

From my recollection off of the top of my head, all of the -8 engines use the same gears.  I will go out the hangar tonight and look to see if the A-65 crank and cam drops into a C85 case.  I don't recall that there is any spacing difference between the journals, but I have been known to be wrong.  The C-85 crank can fit into the A-65 case, but lots of work has to be done the relieve the case to provide clearance for the longer throw C-85 crank.  All of the mags used on -8 engines are right hand rotation, so no problem there.

The ODs of the lifter bores and internal hydraulic plungers are the same.  The tappet face where the cam rides on the lifter is a smaller OD than the C-85/O-200.  The C85/O-200 lifter will physically fit and work in the A-65 application, but is not legally approved in certificated engines.  There is, in fact an STC'd replacement for the A-65 lifter which is simply a C-85/O-200 lifter with the tappet face OD turned down to the diameter of the A-65 tappet face.

The big problem with the C-85 case would be the smaller diameter of the A-65 jug bore.  The C-85/0-200 jugs have a much larger bore and hold won bolt pattern, so you would need to use C-85/0-200 jugs on the 85 case.

The C-85-8 is nearly as light as the A-65, but definitely has more punch. However, keep in mind the weight factor.  I have flown your airplane and it actually performed as well with 65 hp as my 100 hp firebreather.

If you want more power, simply drop in 75 hp pistons and get the prop twisted to turn 2500-2700 rpm.  I have an A-65 powered airplane that I fly that has a very flat prop- it turns 2700 rpm (instead of the FAA approved 2300 rpm) all day and really climbs.  It cruises about 75 instead of 85, but I'm not in a rush anyway.  I suspect that you could flatten the pitch of your prop and get a nice combination of cruise and climb.  You might want to look into specialty pistons made by Lycon, www.lycon.com.  They build Sean Tucker's engines and they never break!  I've used their high compression pistons in a lot of applications and been very happy.  The high compression pistons are a lot less expensive than bigger cylinders and cranks with greater throw.

Be careful with pushing A-65 too far, though, because it's rods, rod bolts and case are not as robust as the C-85 or O-200.  The couple of A-65s that I have heated up have been specially modified with an extra through stud and welded webbing to beef up the case.

Remember, your A-65 was absolutely one of the nicest running A-65's I have ever flown and maintained, so don't hurt my baby! :)

Harry

[October 2002]


Painting the Engine

> I haven't had the chance to assemble my A-65 yet (still working on the


> wings) but am working on little side jobs as I go along.  I have my
> freshly re-ground (oversize) cylinders and want to prep and paint them.  I
> have access to a scookum sandblaster to clean up the steel fins (it has a
> nice fine grade of abrasive) and plan to clean them up with this after
> suitable masking.  Is there a recommended and locally available high temp
> paint to use?  There is a variety of engine paints at the auto parts
> stores.  How about BBQ paint?  Should I prep and paint the aluminum fins
> too, or maybe treat them some other way?  Any input would be appreciated.

I usually use off the shelf engine paint from the auto parts store. Plasti-kote and others make a wide selection of colors.  Otherwise, the official TCM gold can be had from any Randolph paint supplier like Aircraft Spruce.

I just spray the engine paint on to the clean surface with no priming with great results.  If you want to get fancy, lightly prime the steel parts and etch the aluminum bits with alodine to make the paint stick a bit better. Most of the dedicated engine paints I have used have stuck like glue to the engine with very little prep.

Just to be sure, I will take a look at a couple of engines that I have overhaul to see how they are holding up.

Harry

[November 2002]


Low Oil Temperature

The oil temperature on my A-65 seems to be quite low compared to what I'm used to seeing with other engines. It will rarely get much over 120 during touch and goes and not much over that in cruise. I replaced the oil temp gauge and sender and am still getting the same readings. Any thoughts?

What is the outside air temperature where you are flying?  I'm guessing not too cold, but as you get below 40F the oil temp will drop significantly and it is not unusual to see 145F-150F on an A-65 in a Champ.  You don't want to get the oil too cold as it will not flow properly and water absorbed into the oil can't boil off, which could corrode the internals of your engine.

First step is to check your sender.  This will be located in the back of the accessory case.  Boil some water, drop in the sender and monitor the temp on the gauge.  The reason you use boiling water is that water boils at 212F, and even off boil for a few minutes will stay in the 185F-190F range.  If your gauge reads 120F to 140F after being dropped into boiling or just removed from boiling water, then the sender or gauge is bad.

Has the oil temp always been low?  Is your oil pressure relatively high? Usually, oil pressure will remain a bit on the high side with  low temp, high viscosity oil as it requires more pressure to push the relatively thick oil through the lubrication system.  Low oil temp and low oil pressure usually do not go hand in hand.  Typically, you will see high oil temps with low oil pressure which indicates oil pump or main bearing issues.

Do you have an open type Cub cowling or is it more enclosed?  The open cowling simply lets more cooling air through and may need to be closed up. First step in raising oil temp would be to close off the inlet in the cowling the allows air to circulate around the engine or oil cooler.  On the Champ I fly, I have to put some duct tape over an inlet to block off airflow and allow the temps to rise a bit.  Most Cessna 150's in the frozen north where I live will have duct tape over the oil cooler inlets and even restrict half the airflow in the cylinder openings when the temps are consistently below 32F.  Without these cold weather "kits" the O-200 never hits operating temperature.

Next, identify whether or not a cooler is installed.  Some of the A-65 type engines used a cast radiator that attached to the front of the engine.  It may be necessary to remove the cooler from the system or at least block off airflow to the cooler.

It's a stretch, but I have seen some mods to the oil sump to increase oil capacity, and thereby, cooling.  The O-200 and A-65 have different sized and shaped sumps, the O-200 having more capacity.

Harry

[November 2002]


A-65 Parts Sources

Beyond my own collection of parts, I have a couple of other sources for A-65 parts.
Greg Dart in MayvilleNew York always has a large collection of A-65 and airplane stuff in general.  Phone 716-753-3553, 716-753-3553 or e-mail him at Nn9588@netsync.net.  Greg is one of the first guys I call when I'm looking for small Continental parts.  If you go to www.Barnstormers.com (not www.Barnstormers2000.com) you will find an event tab.  Scroll down and find the Father's day fly in info for Dart airport and you will get a feel for his down home support of aviation. I bought my first Fly Baby from him, now that I think about it.

Another source is Woody Herman, 1800-279-3168.  I have never had a bad experience with Woody, but a couple of friends weren't real happy with some of the stuff for a variety of reasons.  Woody has bought and dismantled a bunch of A-65 and some of the parts are a known quantity and some aren't. He has an engine shop in Minneapolis yellow tag some of his stuff and charges accordingly.  Woody is a character (big surprise in aviation) but has done ok for me.  I think that Woody got his start by buying homebuilts like Fly Baby's for the purpose of salvaging the engine.  The aviation equivalent of Soylent Green for you science fiction buffs.

El Reno in Oklahoma is a long time reputable source, 800-521-0333.  They are kind of pricey, but reliable.  Their big problem is that they don't have as many large component parts as they have in the past.

Finally, Fresno Airparts, 559-237-4863, is a pretty good source, also.  Kind of a quaint business, they conduct all transactions via cash, money order or check, so be patient.  They got in some trouble a while back for bogus parts, but I think that they have purged all of that stuff from their system.

There is one final mythical character who no longer supplies parts, but did for many, many years who deserves recognition.  Lou Liebe was out of the Fresno area and reportedly bought a gigantic supply of A-65 parts after WWII.  He sold these parts for dirt cheap prices through out the 60's 70's and 80's.  Lou never advertised and only conducted business through the mail.  In fact I still have some letters of correspondence with him.  I'm not sure if anyone ever actually saw his stash of stuff, but it was reported to be like King Tut's tomb- full of wondrous things A-65.  Lou actually called me once and thanked me for recommending some large customer to him. I had an absolutely delightful conversation with him about the little A-65s. Unfortunately, Lou passed away a few years back and I think that his remaining stock was purchased by Fresno Airparts.

I do have one treasure trove of parts that I'm keeping quiet as I hope to buy it one day.  On one of my international trips I stumbled across a bunker with around 60 A-65 engines removed from a fleet of aircraft for an 85 horsepower upgrade back in the 50's.  The owner has too high of a price on his collection, but it was still safe a year ago.

I'm always looking to add parts sources to my database, so let me know if there are any others.

Harry

[November 2002]

RJW Note:  Harry later added a reminder that any part that is not yellow tagged should be inspected before being used.  "Just because a part looks good, doesn't necessarily mean that it is in perfect condition- common sense just dictates that unknown parts be inspected to verify condition. "  Remember, "Yellow Tagged" means the part has been inspected and is airworthy, "Green Tagged" means the part is rebuildable (but shouldn't be flown in its current condition), and "Red Tagged" means the part is trash.


Cowling and Baffling Drawings

I found all of the drawings required to copy all of the eyebrows, cowling, brackets, etc. for the Piper Cub cowling at the Piper Cub club website. There is a nominal fee for all of the drawings.  You will have to scroll through the parts listings, but it's all there.
http://www.cub-club.com/BlueprintListWeb.doc

Harry

[November 2002]
[The "nominal fee" Harry refers to is basically just a copying and postage charge...$10-$20 or so, depending on the drawing]


Removing Starters on O-200 Engines

> One thing I did straight away was to remove the O-200's starter motor and


> the battery that powered it. That's thirty pounds gone at a stroke!
> Unfortunately I have since heard by hearsay that I need to blank off the
> bush for the starter's shaft because it has an oil feed to it. Apparently I
> shall lose a lot of oil pressure if I do not do this.

About 15 lbs of weight can be saved by removing the starter from the C-75-12, C-85-12 and O-200 (the six cylinder C-125, C-145, and O-300 also use the same starter as the small four cylinders).  There are three types of OEM starters for the small Continentals:  key start, pull cable type and the venerable Armstrong starter.  B&C Specialties and Sky Tec make replacement starters that are more economical, stronger cranking, and eliminate the troublesome Continental starter clutches.  The Armstrong starter is supplied by the pilot, and aside from the occasional between the ears glitches, works reasonably well.

The key start starter has a pinion shaft and clutch arrangement that rides in needle bearing mounted in the case halves of the crankcase.  If an existing starter is removed, the bearing must also be removed and a plug installed to block off the oil flow that lubricated the bearing.  If the oil flow is not blocked, it's akin to a leak in an artery and insufficient pressure will be developed.

The pull cable type starter uses a clutch that rides on a shaft and plug that is captured in between the two crankcase halves.  This drive did not require an oil pressure feed as the mechanicals for this system were bathed in oil splashed around the accessory case. When a pull cable starter is removed, the clutch and drive gear mechanism is removed and the supporting shaft simply left in place.

If an engine is undergoing assembly, and the intention is to not use a starter, be sure to plan ahead!   Inspect the starter bearing or shaft support hole for an outlet for oil flow.  Cases originally configured with the pull starter shaft may or may not have the oil feed hole, depending upon date of case manufacture.  Don't take it for granted you are ok if you have a pull starter- confirm whether the oil hole is present.

If there is no oil hole, you don't need to worry about oil pressure, but popular thinking suggests that the base of the shaft support does serve to keep the two halve so the case from shifting.  Without the plug in place, there is the potential for the case halves to creep and cause fretting.

The best method is to retain the clutch shaft, but cut off the shat prior to installation just in case a decision is made to revert to a starter at a later date.  Some of the lightweight aftermarket replacements require that shaft be cut flush with the case and it is easier to make the mod during engine assembly than after the engine has been put into service.    A similar installation can be accomplished by installing a purpose made plug sold by B&C or by machining up a plug.  Keep in mind, if you are working on an engine retaining its Type Certificate conformity, the Continental shaft or B&C plug are the only off the shelf approved parts.  Any non-PMA or STC approved field mod must go through the FAA form 337 process.

Another method, if you want to avoid using an aluminum plug, is to block the oil galley using a machine screw plug and loctite to prevent the screw from working free.  But keep in mind, the case halves may be subject to fretting.

Ok, that's great, but what if your engine is assembled and you have made no provisions to plug the starter hole oil galley?  Using epoxy to plug the holes is iffy as the  epoxy plug may be blown out by the oil pressure of the system.  A more practical solution is to make a plug of aluminum a little oversize to the starter bearing/shaft bore.  Chill the plug (I usually do engine work in the winter, so where I live in Southern Wisconsin, I simply leave the parts requiring chilling outside overnight) and drive it into the bore using a brass or aluminum drift.  If possible, loctite the plug and use a chisel to peen a mark between the plug and the case.  For the most part, three or four opposing chisel indentations will be sufficient to keep the plug from working out.

Harry
[November 2002]


O-200 GPUs as Fly Baby Engines

(May 2003)
Harry - talking of Lycoming GPU's, I've seen various Continental GPU engines advertised recently on e-Bay and Barnstormers,  4 and 6 cylinder versions.  Do these engines have any  success flying and do you know if their parts fit our A  and C series engines?

There is a GPU that uses many O-200 components, but is not exactly an O-200.  The GPU is single ignition, with a bed type engine mount frame cast into the crankcase.  The cylinders are set up for a single spark plug and are configured with a downdraft intake.  The carb is not an aircraft type and is monted vertically on top of the engine.  The crakshaft flange is a littel different that the aviaiton type- centering cone used on the aviation crank is missing and bolt studs instead of threaded inserts are installed.  I'm not positive, but the cam may be the same between the GPU and O-200.

The good news is that the bearings, rods, rockers, gears, pushrods and all of the little stuff is the same as the O-200, albeit, the GPU parts were not inspected to aircraft standards.  I have purshased new GPUs just to salvage the rods, bearings, etc, for homebuiult O-200 overhauls.

The GPU case could be used, but the case would need to be lightened by cutting off a variety of mounting pads, removal of unused studs, etc.  The updraft cylinders and intake could be used in conjunction with an Ellison throttle body or Altimizer carb.  The GPU crank could be used, but the flange studs would need to be pressed out and the threaded inserts used for aircraft props be installed.  Two mags can be installed on the engine, but the cylinders are only drilled for one spark plug.  A second hole could be drilled for a plug, but it would take some work.  Aircraft cylinders could be installed on the GPU case, but the intake would change to an aircraft updraft type and all of the intake bits for this setup would need to be scrounged.  The GPU is also a dry sump engine, so an oil tank would need to be fabricated.  I saw one conversion where the oil tank was also used as a source of cockpit heat.

I think that the GPU is not a bad choice and could be converted fairly easily by changing the flange bolts, using a flange reinforcement liek the O-290-G, and some cutting to remove excess case weight.  As far as the single ignition goes, it is not likely to be a problem as virtually all VW engines are single igntion and Slick  makes 90% of the ignition systems.  In nearly 20 years of  working for Slick, I have only heard of two events of  igntion problems with VW engines and these two events were  related to lack of maintenance.

Bottom line:  GPU O-200 is a nice source of parts or not  bad for an aircraft conversion.  A GPU can still probably  be found and converted for $2000 or less.

Harry


Mags for the A-65

(March 2003)
I have a chance to pick up a set of slick mags w/harness  for a reasonable price for my A65/A75 engine. He has two separate sets one set is #4370 and the other set is #4251R They both were for 4 cylinder engines.  I don't want to  get a set  that won't work on the A65.  There is no STC for the A65 for these mags but it's going on an experimental (Flybaby).  I have the gears from an old set of useless Catapiller mags.I know Harry would know but was hoping that someone out there can help me without bothering Harry.  Seems like he gets enough problems without this.

Any thoughts, guys??

Don't worry about bothering me, this is the fun stuff!!

The 4251 and 4370 fit the Lycoming 0-320 series.  These are left hand rotation magnetos and the A-65 requires right hand rotation magnetos.  The rotation of the magnetos cannot be reversed.

The only magnetos that bolt up to the A-65 are models 4302, 4230, 4330 and 4333.  There are some military surplus magnetos, model 4220, that are sold cheap and claimed to fit the A-65, but they do not.  Anything is possible with a machine shop, but once all is said and done, it is most cost effective to just purchase the correct magneto kit and have it over with.

As far as gears go, here is the story:  The 4230 and 4330 are impulse coupled magnetos and require the Continental p/n 36066 magneto drive gear.  Because these mags are impulse coupled, the gears from non-impulse magnetos will not fit.  The impulse couplings of these mags also require a spacer to allow the magneto to fit the engine with this impulse coupling and gear arrangement.  The price of the gears are a shocker though- nearly $500 each for the gears!!  Used gears can be found, but be wary as there were bogus gears floating around for quite some time that became the subject of FAA Special Airworthiness Information Bulletin SAIB ACE 98-21.  For reference, the 36066 drive gears are the same ones used for the 4201/4301 magnetos that fit the O-200.  The impulse gears attached to the Bendix or Eismann magnetos that fit any Continental with a -8 suffix will not fit any Slick magneto.

Details of this installation can be found in Slick Service Letter SL1-93.  For the most part, this installation has been superceded by the much easier to install and lesser expensive K4334 ignition upgrade kit.

The K4334 kit consists of two impulse coupled 4333 magnetos, Slick manufactured drive gears, shielded ignition harness and spark plugs.  The gears provided are unique and only fit Slick mags.  The K4334 eliminates the expensive and clumsy spacers so that the installation is more of a bolt on affair.  Details of the K4334 kit can be found in Slick Service Letter SL2-94.

The 4302 is a non-impulse magneto kit that can use the gears from any non-impulse coupled magneto that fits the four cylinder Continental series.  Slick Service Letter SL3-91 covers this installation.

I will get with Ron and provide him with the above mentioned documents so that he can post them at the website for future reference.  If anyone needs a copy right away, just e-mail me your address or fax number and I will send it right away.

Harry


Cold Weather Oil Considerations

(December 2002)
While digging through some engine parts at my hangar today I made an interesting observation.  It is a balmy 25F today and was down to about 7F last night, so the hangar was still cold as a tomb at lunch.  I was messing with a crank from a disassembled engine that still had the rods attached.  I almost couldn't move the rods due to the stiffness of the residual 50 weight oil!!  Out of curiosity, I grabbed my fish scale and to observe the pull required to over the rods.  It required a 12-15lbs pull to displace the rod 90 degrees.  Once the rods had been turned a dozen times the pull dropped to about 8lbs, but it was still very high.

I opened a can of 50 weight oil that had been cold soaked and it had a thick, wax-like consistency- definitely not good for lubrication!  The 20w50 synthetic was better but still very sluggish to pour.

What an eye opener!!  There is no way that I would fly again without preheating if the temps were below 45F.  Positively, there is no way I would fly with 50w in the engine below 50 degrees as I just can't see how it can be pumped through the engine.

I'm going to take my crankshaft home and conduct some tests over the next few days with various oils and report back.  Basically, my idea is to remove the rods, lube each journal with a different weight and type of oil and record the pull required to complete one revolution of the journal.  I'm not sure what it will prove other than reinforcing the need to use the correct weight oil and to preheat.

Harry


Some Thoughts on Alternate Oils

(Dec 2002 - this started as a response to Harry's note about cold weather oil considerations...)
A Fly Baby Mailing List member wrote:
I'm sure using non-aviation oils is controversial for some but I'm happy to use it.  When I was restoring my FlyBaby in '95 I was working in the Navy  Dockyard.  I had access to the engineering library and researched  lubrication oil.  Basically what I came up  with was that the cheapest multigrade SG service rated automotive oil sold  today is light years ahead of any oils refined in the 1950's, back when our engines were new, which was as far back as I could find any oil service ratings.  SL diesel rated multigrade oils would probably be great too.  I was using aviation mutigrade oils but  switched to a major brand of automotive mutigrade in my A-65.  The plugs ran clean and the engine ran fine and actually used less oil.  I could do an oil change every 15 to 20 hours for the cost of one litre of aviation oil.  There's a Kinner powered Fleet in my hanger which has used automotive 15W40 ever since it's restoration with no troubles at all.

Luckily, I've had the pleasure of working with Exxon and Aeroshell on various projects and I have picked up some good info on oil.  The primary difference in aviation oil are additives that prevent corrosion due to contamination from leaded fuels.  Other than that, av and auto oils are very similar in viscosity and formulation.

I have used auto oil in small Continentals and I agree with Drew that the old grade oils were inferior. I have not observed any obvious problems using auto or motorcycle blended oils in the small Continentals.  My favorite non-av oil, due to flow and rust inhibition characteristics, is Shell Rotella T, but I have used everything with virtually no problems.  I change oil every 25 hours, so whatever I put in usually never really gets pushed to its limits.  You can throw a cat through some of the tolerances found in the Continentals, so the small fours are very tolerant of wide range of lubricants.

However, sometimes what I do and what I recommend are two different things. I always caution that engine manufacturers do establish specs for a reason, and the relative cost difference between auto and aviation oil is not that great- maybe $1.50 per quart.  For our Canadian friends the cost difference between auto and av oil is probably about US$20 per oil change, whereas in the States it is only about US$8-$10.  For the conservative minded, it is sometimes a small price to pay to stick with established products with a known history.  I accept the risks when I stray from established practice and if something goes wrong, I take the blame.  I don't mind offering advice, but there are times I don't want to be the lead Lemming, either- motor parts are expensive!  As always, define your goal when straying from established practices- are you changing for the sake of change, experimenting to learn, or just trying to save a buck?

Be aware that some engines are sensitive to non-aviation oils.  The Lycomings, in particular, will suffer problems if auto oil is used.  Both Exxon and Aeroshell incorporate a special additive that helps reduce spalling of cams and lifters.  Also, some older bearings that use silver as a component will disintegrate when modern auto oils are used.  I have heard that some oils will have a detrimental effect on certain six cylinder Continental valve guides, but I don't have evidence to back up that claim.

On a reciprocal note, don't use av oil in auto engines!  I did this once and wrecked an engine in my 70 Mustang.  The av oil caused huge amounts of sludge buildup that eventually clogged all of the oil galleries.  Must have been something to do with the detergents in the av oil.

And don't get me started on Slick 50 or any of the other super-lubes!  The bottom line is that all of these oils use a Teflon component, and there is no doubt that Teflon reduces friction.  The problem is, Teflon is a particulate and may not remain in uniform suspension in the oil.  The Teflon flakes can precipitate out and "flock" or clump together.  Flocking is more pronounced during colder ambient temps.  Flocking can be severe enough to restrict oil flow through smaller passages.

Finally, I have to mention the Mobil AV1 fiasco from a few years back. Mobil 1 is a synthetic oil for auto use that has had a pretty good track record.  Naturally, Mobil expanded this formula into aviation use with some additives to counter the corrosives from leaded fuels.  Mobil really hyped this oil, especially for use in the turbocharged Continental and Lycomings.  The engines that used the oil literally wore out or sludged up within a few hundred hours and there was a massive recall.  It turned out that some of the oil additives were not compatible with some of the materials used inbearings and valve guides, and these parts disintegrated and plugged oil passages.   Mobil eventually wound up overhauling several hundred enginesthat were damaged by the oil.

Harry


What about the Franklin 90 HP Engine?

>What can you tell us about Franklin engines, particularly the 90 hp?
The Franklin engine generally works ok, but is generally recognized to be a weezy 90 hp engine- it just never had the same oomph of comparable Continentals.   The Franklin company went bankrupt 50 years ago and no parts have been made since, and aggravating this problem is that there are very few people left who know how to work on them.  Valves and bearings are in short supply, but I'm sure that substitutes could be cobbled up for experimental use.  Don't even ask about gasket sets!  If you are of a mindset to tinker, then the Franklin is not a bad choice.  However, if you want a cheap, turn-key engine, the Franklin is not a good choice.  From the practical standpoint, an extinct engine with no support is not a great choice for daily, no worry flying.  I would probably pursue the Corvair route before a Franklin- at least you can get parts and support for a Corvair.

I've said it many times before, you may pay more for an O-200 up front, but when the day is done and the aggravation is tallied and the dollars are spent, the O-200 will cost less and be more reliable than just about any other powerplant.  Even the A-65 can still be found in fairly good supply, but after messing around with finding a good crank, case, and rods, it is probably just as cheap to get a runout O-200.

Harry

[May 2003]


Trouble-Shooting Low RPM

I bought an engine with 50 hours from overhaul that was on a homebuilt, that I flew a couple times.When I put it on my Cub I'm only getting 2000 rpm. I tried what seems like every thing. I'm beginning to think about valve springs. Anybody have any idears?
Here are some questions for you to help fill in some blanks on the performance of your engine.  Some of the questions may seem basic, but start with the obvious questions first and then move forward:
Once all of the above is sorted out, then remove the carb and take it to a shop to get checked.  The carb is pretty simple to service on the bench, but I have found that the trained eye of a technician who works on 20 carbs each day will probably yield better results than my once a decade exploratory.
Ok, now on to your comment on weak valve springs.  This is probably the least probable source of your problem, but another part of the valve train could kind of support your thinking.

The purpose of the springs is to aid the valve to open and shut to keep the airmass of the  mixture, compression, power and exhaust strokes in the correct  chamber during the combustion cycle.  For example if the intake valve bounces open during the exhaust stroke, then the intake mixture backfires into the carb or intake system with a very muffled metallic sound.  The result is a power loss.  An exhaust valve open during the compression stroke results in a power loss.  The mixture will probably ignite, but burn as it exits through the exhaust system.  You do have a digital, multi-point engine analyzer in your Cub, right?  :)

At rpms above 3000, floating valves and weak springs can be an issue.  At 2000 rpm, I'm willing to wager that they are not.  If the springs were floating, your engine would be backfiring and making all sorts of noises. Been there when valves floated in my Cassutt O-200 engine one day at 3600 rpm backfiring like a Thompson submachine gun into the intake. Hooo-weeee! The effect of floating valves is not subtle- all of the connecting hoses were blown off of the intake.  Another feature with floating valves to consider is that the condition should change with rpm,  Reduce rpm and the effect should lessen or disappear.

You mention that the engine has 50 hours- how many calendar years or months ago were the 50 hours accrued?  If the engine sat around for a few years, the hydraulic lifters may be gummed up.  If the lifters are not pumping up, then engine performance will suffer.  Once again, kind of a long shot.  The hydraulic lifters can't be serviced without removing the cylinders.

One final comment:  you mention that the engine came from a homebuilt.  Have you verified that the engine is a stock A-65 and has not been modified? This is a real problem with salvaging engines from homebuilt, especially if the engine is acquired from an estate sale where the wife or relatives may not have a solid history on the engine.  We have a lot of latitude in the Experimental world, but there is a reason that the FAA requires that the engine dataplate be removed from the engine when it is modified from a Type Certificated condition.

Let me know how it goes to see if my troubleshooting advice actually works!   I'm thinking that the tach, mag timing, or the prop pitch is the culprit.

Best regards,

Harry Fenton
[May 2003]


A-75 Connecting Rod Nuts

I have a question that I can't find in the Archives! So if this has been discussed before, forgive me.
I am putting the A75 back togeather. Does everyone still use the  cotter pins on the Connecting Rod Nuts?  My old manual shows them but  I seem to remember that on Lycoming there were some AD's to the  effect that it was better to torque to exact than line up pin holes.   On two of them, I am half way between.  It just doesn't seem like the  place to add thin washers or overtighten!  You have to understand that this is my first overhaul and I'm surely  not the brightest bulb in the room.  The engine was a basket case so don't know what the last guy  did...well, actually I do know what he did...He ripped everything apart and left it in a couple of bushel baskets in the loft of his  barn about 40 years ago.
Maybe some intellegent thoughts out there?

Yes, the nuts used on Continental connecting rod nuts must be cotter pinned!!  I think that the Locoing bolt and nut arrangement that you reference are the "stretch" type bolts used by Lycoming.  The stretch bolt was a combination of special self locking nut and special bolt that was not torqued, but tightened to length.  As the bolt was tightened, it stretched, and when at a proper length, was at proper torque.  The self locking nut kept everything locked in place.

If the castellation doesn't line up within the torque range, remove the nut and polish the mounting face with scotchbrite or lube to reduce friction.  I have yet to see a nut and bolt where the castellation won't line up in the torque range.

I'm often asked about using alternate fasteners on engines, especially connecting rods (usually due to cost).  As experimenters, anything is can be tried, but a connecting rod bolt is pretty important, and the stock hardware rarely, if ever, fails.

Harry Fenton
[January 2004]


A-65 Oil Pump Loses Prime

I have a continental A65-8 engine it had a certified major overhaul in August 2000 it now has 75 hours since overhaul. My question is when I change oil drain the sump I have to reprime the oil pump thru the oil screen or it will not pick up the oil.
Once this is done then the pump seem to hold the prime and as long as I run it every week or two weeks all is ok.  However this last  weekend it sat idle fore three weeks while I replaced the fuel tank.  When I  went and started the engine no oil pressure until I removed the temp prob from  the screen housing and shot oil in there to prime the pump again.

During flight, oil pressure is 30 to 35 lbs and temp runs 180 to 190 degrees.  At idle, oil pressure is 10 psi cold engine pressure is 50 to 55 depending on outside temp.  I am using Phillips 20W50 oil.

Any thoughts on what is causing the pump to loose it prime after sitting a while?   Could it be the cover plate on the pump or maybe the tach seal (seal seeps some)?  This engine is on my flybaby, the 65 cont that was on my Luscombe would only need priming after draining the sump and I would fill  the screen area and it would hold it for months

Any ideas will be appreciated

Oil pump problems are one of the most common problems with small Continentals.  The A-65 is a real stinker just because no new accessory cases are available and what is in service is usually 50-60 some odd years old.

My first thought is that the edge clearance between the pump gears and housing is probably excessive or the housing cover may not be flush with the mating surface of the pump cavity.  I spoke with tech reps from TCM and Mattituck and they both agreed with my opinion.  The oil pressures are ok, but the idle pressure, while in limits, may be a tad low.

The only way to tackle the problem is to remove the accessory case to access the oil pump.  The ID of the oil pump pockets not only needs to be in spec, but the surface of the bore should not show excessive wear.  It is normal to see some strike lines from FOD going through the pump, but if the surface is marred too much, this will increase the edge clearance between the gear and the pump well walls. Also, while the gears are accessible, measure the backlash of the gears to ensure that they are in spec.

Many times, the cover for the oil pump simply isn't seated square on the housing or is a bit warped.  A common fix is to lap the mating surfaces between the oil pump cover and the oil pump housing using a valve lapping compound.   There is a chance that just improving the seal between the pump and the cover will help the problem.  The only problem is that the accessory case may have to come on and off the engine a few times, which is no small task.

I doubt leakage at the tach seal is contributing to the problem, but the tach seal housing is very easy to access and the seal is cheap, so why not replace it.

It is very likely that pump bores may need to be re-welded and re-bored.  I think that Drake Airmotive or Aircraft Specialties out of Tulsa has a process for doing this.  The A-65 case is magnesium and is kind of touchy to repair.  There is a risk with sending the case out for
welding- if the copper content of the magnesium is too high, the part cannot be welded.  So, you may have a case that is marginal to acceptable, but if a repair is initiated and it is found not to be weldable, then it becomes junk.  I use welding as a last resort on the A-65
case.

Soooo..  if you are budget minded and don't mind the time and labor of pulling the accessory case from the engine a couple of times, you can fuss around with the oil pump cover plate.  Be prepared to take the cover off a couple of times to experiment with seating the cover.  If the cover doesn't solve the problem, then the culprit is the oil pump pockets.  New gears may solve the problem, but it is most likely that the pump bores are out of spec.  If the bores are bad, then an alternate case or a repair to the existing one is the only solution.

Harry Fenton
[October 2003]


Exhaust Gaskets and Exhaust System Repairs

Which type of exhaust gaskets would most people recommend?  My A65 had the two types.  I prefer the wider asbestos type gasket but have no experience on these little Continentals.
I have a broken exhaust system flange and dropped the stainless pipes yesterday.  My plan is to order in a ss flange and have it welded on.

For small Continentals, my favorite gasket is a type called the “blow proof”.  The blow proof is simply a pair of stamped metal gaskets that nest together when compressed down.  An alternative type is the spiral metallic, which feature an embedded spring in the ID for sealing, but these work best for new or overhauled cylinders and exhaust system combinations.  Asbestos type gaskets are my least favorite as they seem to blow apart with relative regularity.

Some comments on exhaust system repair.  There is a stack up of tolerances that can occur between the mating surfaces of the cylinders and the mating surfaces of the exhaust.  If you were to draw an imaginary line across the exhaust flange surfaces on one bank of cylinders, they will not be square. Conversely, the same is true of the mating surfaces of the exhaust.  If you factor in that the cylinders are independently mounted and shake around at different frequencies, it becomes clear that there is a lot of slop in the system.

Which brings me full circle as to why I prefer blow proof stamped gaskets. You can stack them up as needed to shim the exhaust system square to the cylinders.  The spiral metallic gaskets work ok, but are less forgiving of worn mating surfaces.  The blow proof are also less expensive:  $12/set versus $12 each for spiral metallic.  Asbestos gaskets have some “squish” which allows for taking up some of the tolerance slop, but cost more than blow proof ($5 each) and don’t seem to last as long.  The Blo Proof brand is a copper composition gasket, whereas the same design can be found as a plated steel stamping from Superior or TCM for a dollar or so.  These are my choice as they are cheap and work well.

Now, as long as you have your exhaust system off, inspect the various mating surfaces.  Some erosion is normal as 1200-1400F exhaust gasses salted up with corrosive post combustion byproducts are in the immediate vicinity. Inspect the exhaust pipe flange for pitting, erosion and warping.  If the erosion extends more that half way into the flange, then the flange should be replaced.  If the flange is worn more than half of its original thickness, then the flange should be replaced.  If the flange requires replacement, inspect the pipe for integrity.  Test external pitting with an awl to see if the surface holds together.  Ironically, the best part of the pipe will be at the flange end and the worst at the outlet end.  If the outlet is rotten, scrap the pipe.  It may be possible to patch the pipe by scabbing on ends or flanges, but weigh the economics of replacing the entire pipe versus patching (yes I know, the audience is frugal by nature, but I have to clear my conscience).

If the cylinder surface is worn it can be faced by an engine shop. Unfortunately, it is not easy to field repair worn cylinder exhaust faces. Some wear is acceptable, but it is a battle of diminishing return.  The more worn the face, the less likely it will seal, the result being greater erosion due to exhaust gas leakage.

When an exhaust system is removed, the hold down studs sometimes will screw out.  I typically install new studs with a drop of red Loctite to hold them in place.  If standard studs are too loose, oversize studs are available. If the threads pull out of the cylinder, then can be helicoiled.  Easier said than dome as the cylinder really needs to be pulled from the engine to install the helicoil properly.

Finally, install brass exhaust nuts when reinstalling the exhaust system. The brass nuts do not corrode, are taller, providing more grip than a steel nut and are just simply easier to install and remove.  Related to this, the best tool combination to remove nuts is a ¼” drive deep well, ¼” universal joint, ¼” drive 12” long extension and ¼” drive ratchet.  Sometimes, due to clearance, a ¼” drive swivel socket may need to be used in place of the standard socket and universal joint.

Some thoughts on the Aeronca style exhaust installed on your engine, though.  I don’t think that you can weld stainless flanges to carbon steel.  I can’t remember if the stacks on your plane are chromed carbon steel or stainless.  Second, the Aeronca stacks tend to crack at the V where the two pipes come together due to the differing rates at which cylinders vibrate and thermal cycle on the engine.  A common fix is to weld a strap above the V to take the flexing stress off of the V.  If you have access to a Univair parts catalog, this strap is illustrated with their Aeronca exhaust.

Overall, stainless exhausts are the best for durability, carbon steel are the best for cost.  I figure that the lifespan for a carbon steel system is about 10 years and stainless will last 30 years or more.

Harry Fenton
[February 2004]


Exhaust Stack Expansion Joints

(This was a follow-up to the above discussion)
The stacks are stainless as they are not magnetic.  I think a rear expansion joint is in order.  After your note Harry I looked carefully at the flanges and they are burnt so new flanges up front and flanged stubs in the back with expansion joints are the plan.

Sounds like an easy repair.  Don't remove the flanges before the welder can build a jig to orient the flange on the stack.  I just did this last month working on the exhaust on my C125 Continental.  I carefully ground off the old flange and welded on the new one.  And then realized that the flange and the bend of the pipe were all wrong when I tried to install.  Doooohhhh!!

I wouldn't worry about an expansion joint as the Aeronca exhaust is surprising durable.  A little strap welded between the pipes just above the vee works pretty good.  One of the problems with slip joints is that they continually leak.  I'm going to install Aeronca stacks on my Fly Baby during the rebuild to save some weight over the Hanlon Wilsons that are currently installed.  Although, the Hanlons really belted out the heat on slightly chilly days....

Harry


A65 Quits on Roll-Out

On roll out, my A65 engine quits.  The engine is an A-65-8 with Eisemann mags---rebuilt, seems to be good rebuild and will throw 3/8" blue spark on bench.  Carburetor is a Stromberg Nas3- it was rebuilt buy a carb shop. since then, we have had it apart and checked float level. all passages are clean, jets are the right size, and visually it seems like it is good. It has a plastic needle and new seat, We also tried a steel needle and new seat. All AD's and notes have been complied with on this carb. We have idle set to 550 to 600. after landing in three point roll out the engine will quit nearly every time. engine will quit when taxiing in, if idle speed gets too low.
We try to keep it 800 or above to keep from dying, Plugs are wet and it seems to be a low rpm mixture problem. once it decides to die, it is just like you turn off the mags switch. It can't be caught and brought back. When you go to start it, without touching anything, it will catch on the third blade and run real goo for a few minutes like nothing ever happened, then die unless you keep it reved up a little. Black smoke will puff out at the lower rpm's when you throttle it up. This indicates excess richness at idle setting and the wet plugs do too. when we lean the idle mixture to stop the black smoke, it will pop indicating too lean of an idle mixture.

Static runs are good, no missing and it turns about 2100 to 2200. Mag checks are good, maybe 25 or so drop on both mags. I would call it good.

In the air at cruise, it is just great. When first starting here in the midwest at this time of year, it is very cold natured. Maybe have to start it two or three times to get it going and keeping it going. We have been running av-gas, premium car gas, and non alcohol regular. seems like the same thing with any of the fuels.

We also get small fuel drips at shut down for a couple of minutes. This doesn't seem bad, but I know that all 65 hp dont drip like this and I feel there is a relationship between the drips and the richness.

The engine has about 100 SMOH and runs great above the intermediate RPM's. it is just the low RPM problem that is bothering us.

To set up the idle on the Stromberg carb it is a procedure of balancing the idle mixture and the idle speed set screws.  The idle mixture is a slotted thumbscrew half the size of a dime located at the top of the carb body facing aft.  The idle speed mixture is a small set screw on the arm that the throttle cable attaches to.  The idle speed can be set just using the idle set screw, but the mixture may be wrong and the engine can run too lean or too rich at idle, resulting in the propeller stopping.

The set up procedure will require that the engine be started and stopped several times.  Don't attempt to set the idle with the engine running! Invariably, you will be coached by some guy who will insist that the idle be set with the engine running, but the danger of working around a spinning prop is too great.

The first step in the procedure:  Does your tachometer read correctly?  It is not unusual for 60 year old tachs to read incorrectly at idle.  I use an optical tach made by Cermark, a manufacturer of model airplanes and parts. This optical tach runs $50 or so, but it is a very useful special tool to keep in your toolbox.

The engine idle should be 550 to 650 rpm.  Veteran Cub owners will suggest that idle be run down as low as 350 rpm.  This was possible with non-impulse coupled Bendix SF series mags, but too low for any impulse coupled magneto  If it is too low then the impulse couplings on the mags will engage and the engine may quit at idle and the oil pressure may be too low.  If it is too high, the airplane will probably run you down on start up.   The idle may need to be set 50 rpm high due to the low inertia of the wood prop.  Metal props have more weight, therefore more inertia, so may need a bit less idle.

Start the engine and observe the idle.  Gently run the throttle back and forth to find the idle position of the throttle.  There is a bit of "springback" in the throttle control rod and cable, which can affect idle. The throttle should always be positioned so that the stop is the set screw on the carb body, not the contact of the throttle against the airframe.  You may have to adjust the throttle linkage so that there is a bit of rearward clearance between the throttle arm and the airframe.

Next, using the idle speed screw on the throttle arm, adjust the idle to spec.  Start the engine and run the throttle back and forth a half dozen times to make sure that the linkage springback is correct and not interfering with the idle stop.

Now the tricky part:  setting the idle mixture.  This is simple to do with carbs with a mixture control.  When the mixture is pulled to idle, the rpm should rise about 50 rpm just before the engine dies.  The A65 is killed via the ignition switch, so it is difficult if not impossible to see any rise in rpm as the engine leans out and quits. Setting up the A65 idle mixture is often done by ear.  Run the engine, lean the idle mixture.  If the engine backfires when the throttle is rapidly cut, then the mixture is too lean and needs to made rich.

Ok, that's the theory; let's consider your specific situation.  There are some idle bleed holes in the carb that may be plugged or obstructed that cause your engine to die at idle.  Does the engine stumble when the throttle is rapidly advanced?  If yes, then the idle bleed holes may be obstructed. Related to this is a loose throttle shaft to carb body fit.  If excessive air leaks around the throttle shaft, the mixture will lean out excessively and the engine will stumble at acceleration and die at idle.

Disconnect the primer line at the spider and cap it off with a little rubber cap.  The rubber caps are commonly used on automotive vacuum systems and can be bought at an auto parts store.  Vacuum in the induction system can pull fuel through a leaky primer.  The fuel from a leaky primer is burned up at cruise, but is very noticeable at idle and can foul plugs quickly.

Is the carb heat adjusted correctly?  A loose or partially open flapper valve will make the engine run rich at idle and foul the plugs.

How does the engine run without the air filter?  If the filter is restricted, then the engine will run rich and choke from lack of air.

On to the mags:  You mention that the mag makes a blue spark.  Was this checked simply by spinning it or on a test bench with a tach?  It makes a difference.  A mag with a bad coil may make a good spark at mid to high rpms, but won't make a spark at low rpm.  In short, the mag makes more energy the faster the magnetic rotor shaft is spun, so the more energy, the greater the chance that the generated spark can overcome an open or fault in the coil.  Your mags may simply be breaking down at low rpm.  On the bench, you spin the mag until it makes a spark, and it is possible to spin the mag 1000 rpm or so by hand when twisting it quickly.  A test bench is more accurate in that you can gauge the "coming in" speed, or the lowest speed at which the magneto will reliably generate a spark.

Another long shot is park plugs.  The old C26 series, REM40E, REM38 and REM37BY are all good part numbers.  Some of the early Unison Autolite plugs suffered resistor failures which would result in fouling.  Unison changed the design when the problem occurred and very few of the affected plugs made it into service.  I'm guessing that you are not using those, but if you are, let me know and I can give you more info.

I'm thinking that your primer is leaking or that your tach is not reading accurately when you are using it as reference to set up low idle.  Another possibility is that you have A75 metering jets in an A65 carb (although you mention that jet size was checked).  The mags may be at fault, but it is unlikely that both would fail identically at the same time.  Overall, you clearly have too much fuel based upon the black smoke and wet plugs.

Keep me informed of your progress and I'll do what I can to help out.

Harry


Torque vs. Horsepower

I wonder if I could ask for an explanation of how torque and horsepower relate, and why two engines of the same horsepower have different torque values?  Is it displacement?  RPM?  And what makes an engine like the Jabiru "need" a smaller prop?  And why won't a small prop work with a Fly Baby?
Hooo-weee!!  An easy question with not so easy answers, at least not an easy short answer.  The discussion of the relationship and computation of horsepower and torque is a complicated topic.  KitPlanes, EAA Experimenter,  and Sport Aviation have devoted huge amounts of editorial space to these topics.  Needless to say, there is a division in thought between theory and practical application.

The traditional equation for horsepower is RPM times torque divided by 5252.  But this theoretical equation does not take into account factors such as the volumetric efficiency of the engine, pumping and frictional losses, the efficiency of mixture distribution, etc.  Some of the most important design elements that effect the relationship between horsepower and torque are the bore (piston diameter), stroke (the distance that the connecting rod travels from top to bottom of the reciprocating stroke) and compression ratio (the volume squished between the top of the piston and the top of the combustion chamber during the reciprocating range of travel of the crankshaft stroke) and RPM (essentially, the number of ignition events in a given period of time where power and torque may be generated).  As a rule, torque producing engines are designed to be "oversquare", or with a cylinder bore greater in diameter than the length of the stroke.  For example, an engine with a 5" bore and 4" stroke would be considered to be oversquare.  Also, oversquare engines tend to produce torque better at relatively lower RPMs than relatively higher RPMs.

There is a relationship between horsepower and torque.  Generally, the ratio of horsepower to torque yield is more favorable to engines of greater displacement. An engine of lesser displacement simply has to work harder than an equivalent engine of greater displacement to generate torque.  A smaller displacement engine can compensate for displacement by employing higher compression ratios (effectively squeezing in more bang in a smaller space), by turning at a higher rpm (more bangs per unit of time) or a combination of both.

The Lycoming 0-145 is rated at 65 hp at 2550 rpm and 75 hp at 3100 rpm and only 50-55 hp at 2300 rpm.  The Continental A-65 is rated at 65 hp at 2300 rpm, and with some piston and carb mods, rated at 75 hp at 2600 rpm.  A major difference between the O-145 and the A-65 is cubic inches:  the O-145 is 145 CID and the A-65 is 170 CID.  Additionally, the  bore/stroke of the A-65 is 3.875"x3.625" versus 3.625"x3.500" for the O-145.  Although both engines are rated at 65 hp, the A-65 has more cubic inches and a longer stroke which yields about 148 ft/lbs of torque while the Lycoming can muster only about 134 ft/lbs of torque.

The A-65 clearly develops more power and torque for a given rpm.  In very simple terms, the bigger displacement of the A-65 means that greater the volume of fuel that can be introduced into the combustion chamber.  The more the fuel, the bigger the bang, the greater the potential for reciprocating force, the greater the potential to develop torque.  In other words, nothing beats cubic inches- at 2300 rpm the lesser displaced O-145 makes 50-55 hp and the greater displaced A-65 makes 65 hp for a given slug of fuel/air mixture.

But, some engines of large displacement may be rated at lower horsepower and develop more torque than an engine of higher horsepower rating.  Let's compare the 90 hp Curtiss OX-5, the 90 hp Continental C90.  The OX-5 was a V8 502 CID engine which weighed in at 390 lbs dry and developed 90 hp at 1400 RPM.  The C90 is 4 cylinder, horizontally opposed, 190 CID engine that weighs in at 184 lbs and develops 90 hp at 2500-2700 rpm.  I couldn't find torque values at this writing, but I can interpolate the torque characteristics of these two engines by considering the diameter of propeller that each is capable of turning. The C90 will swing a 5-6 foot diameter prop whereas the OX-5 will turn a 9-12 foot prop.  Physics dictates that the bigger prop will require more torque to move, so I can reasonably conclude that greater CID of the OX-5 is winning the torque battle.  For this reason, the lower displacement of the 0-145 loses the torque battle to the bigger displacement A-65

Another wrinkle in the torque discussion is something called the torque curve.  Ideally, for aviation purposes, it is best to have the torque curve, or the magnitude of available torque to generated horsepower, be flat.  In other words, for any given amount of horsepower, the relative ratio of torque would remain constant.  Some engines have a flat torque curve, and as the power is reduced from max output to 75%, the "pull" feels about the same.  Some engines have a "peaky" torque band and when the power is reduced from 100%, the pull really drops off.  Some engines actually make more torque at 75% rated power than 100% power.  Why?  Because engines don't run at 100% power in cruise, so the "pull" is engineered to be optimized for the RPM where the engine is likely to be operated continuously.  The Franklin 4A-235 is a classic example of the backwards torque curve.  This engine has a max rating of 115 hp, but actually  develops more torque at 100 hp.  So is this engine a strong 100 hp engine or a weak 115 hp engine?  Answer: Neither!  Due to the lower power versus weight ratios of the Franklin vs the Continental O200 and the Lycoming O-235, it is theoretically not as good as either engine.  Is the Franklin a bad engine choice, then?  No, it is actually a pretty good engine, just not as good statistically when compared directly to other engines.

Some other comments on why the Walter Mikron and the Lycoming O-145 suffer in the propulsive arena:  rated hp/torque vs RPM.  The A65 makes rated horsepower at 2300 rpm, while the O-145 requires 2550 rpm and the Mikron spins at 2600 rpm to make 65 hp on 149 CID.  Propellers are most efficient at lower RPMs, roughly 1200 to 2400.  Another propeller problem is that it takes torque to spin a large diameter prop.  If the engine can't develop torque, then the propeller diameter needs to be reduced, the propulsive disk area is less, which results in less thrust.  To compensate for reduced propulsive effect, props are sometimes turned at a higher RPM, basically to get more events or chances to bite into the air during a given period of rotation.  But, go back to the beginning of this thought: props are less efficient when spun fast, so the benefits of higher rpm are often offset by the losses.

One final note on engine to airframe application.  The Sonex flys quite well with an 80 hp Jabiru, whereas the Fly Baby is likely to not even taxi very well with a Jabiru.  Why, as both airplanes have similar power to weight ratios?  The Sonex is a cleaner design with much less drag and has a smaller frontal cross section.  Because it is cleaner, it takes less "pull" (torque) to pull it through the air.  The smaller frontal area also means that a smaller diameter prop provide sufficient disc area for thrust.  The Fly Baby is an airframe of significantly higher overall drag, and requires a stronger "pull" to move the drag through the air.  The frontal area of the Fly Baby is not as streamlined as the Sonex, therefore a larger diameter prop is required to provide adequate thrust.

Ultimately, volumes have been written on engine theory and, thanks to the Internet, huge amounts of information is available on the topic. Ultimately, there are engines that look good on a stand alone basis, but don't make the test when put to practical use or are mission limited to specific airframe and mission parameters.  That's why I continually recommend the A-65 through O-200 for the Fly Baby.  The Fly Baby airframe was optimized for the small Continentals and flys best when so equipped. When the day is done, no other engine provides the spectrum of value as the four cylinder Continental.  Cheaper engines may be found, but that will be the only benefit.  More exotic engines may be found, but the offset will be weight, serviceability, or higher cost.  Some engines, like the Rotec and Walter Mikron, are simply fun to look at and listen to.  An old hotrodder mantra is "if it don't go, chrome it!"  Aesthetics sometimes outweigh all other engine performance issues.

Harry


C85 Conversions Using O-200 Parts

I have a C85 on My FlyBaby. I would Like to Convert it to 100  HP. I  know there are STCs  to do this .But I don't need the Paperwork. Do I just


need to Change the Crank,Rods and Pistons to accomplish this?

Due to variations in manufacture of the pistons and cylinder heads that the C-85 piston is not always a drop in installation.  What I’ve found is that the bevel at the top of the piston can vary a bit and the junction at the mating surface between the head and cylinder barrel also varies.  The net result is that the C-85 piston may contact the cylinder head/barrel junction.

The fix is to machine the piston crown a bit to increase the bevel area to provide a bit more clearance.  I’m working out the specifics of what to suggest for the machining tolerance, but it doesn’t look like much, maybe increase the width of the bevel to ¼”.

This was a bit of a puzzler as I had installed the pistons probably half a dozen times with no problems.  The key to my success was that I had always used new parts, both pistons and cylinders- and was lucky on the stack-up. However, I’ve gotten a couple of reports back from guys building engines using used or in-service parts who ran into interference issues.   Luckily, the interference was more of an inconvenience than an operation problem. The crankshaft wouldn’t turn after assembly!

I recommend that the bevel of the C-85 piston be increased to ¼” to provide adequate clearance for the piston/cylinder head/cylinder barrel
intersection.  I’m still working on the specifics, so this is a preliminary suggestion.

Harry


A65 Conversions Using O-200 Parts

[Follow-up question to previous item]
Could A65 rods be used instead of 85's?  Are the C85 jugs the same as the O-200?  Could an A65 Case be used instead of the 85?

Basically I guess what I am asking is if I can convert my A-65 to 108 hp  with an O-200 crank and 85 jugs and pistons. If so, what could I do about the prop to keep keep it close to within  A-65 static and cruise rpm limits while increasing climb performance-  that is what is most important to me, speed in cruise is secondary.
 

The A65 would require a change to the beefier C85/O200 rods.  The lightweight A65 rods are known to break even at 65 hp.  The A65 cam would also not be right for 100 hp.

The studs used to hold the cylinders to an A65 case are smaller than the C85/O200, so you would need to tap and weld the case for the studs for the bigger cylinders.  Likewise, the through studs are lighter on the A65 and would need to be upped in size.   Some of the early A65 cases tended to break the saddle for the bearing near the #3 cylinder- in fact a pretty common failure.

The carb, induction spider and induction tubes are all smaller on the A65 and would require the use of C85/O200 parts.  The rocker arms on the exhaust
side should also be drilled for oil squirt holes to cool the top of the valve stems.

The A65 prop would have to be repitched and probably clipped to let the engine develop more horsepower.  I seem to recall that the O200 McCauley was much beefier at that hub than the A65, but I may be wrong.

In short, nothing is impossible in the experimental world, but the A65 is a poor candidate for 'supersizing".  Converting to an A80 is a much easier and much less expensive alternative as the only significant mods are the pistons and carb jetting.  Or, sell your A65 and buy and throw some extra cash towards a C85 or O200.  The cost of modifying the A65 would probably exceed the cost of a complete C85/O200 anyway.  Or, just use non-FAA approved Venolio or NFS high compression pistons and re-jet the carb to run the horsepower up

Some horsepower gains are easy and some aren't.  Dropping C85 pistons in the O200 is the easiest of all of the small Continental upgrades.  Converting the A65 to a C75 or A80 is the next easiest.  Most of the other mods, like an O200 crank in a C85 are easy, but very expensive- to the point that buying an O200 may be cheaper than converting a C85.

Harry


Bendix SF4 Magneto Repair/Replacement

Left mag went early in my ferry trip from TX to OR. Engine is A65-8  I believe. The A&P says the mag is a Bendix SF4RN-8. I don't see any of  that model in Aircraft Spruce. What are my options?
Getting an SF4 fixed is a tough proposition.  The only company that can really do it well is Savage Magneto in California.  The cost will probably be more than replacing it.

The least expensive method is to install a Slick 4302 and half of the Slick harness (sorry, I?m on the road and don?t have the numbers).  The gear from the SF4 can be used with the non-impulse 4302.  The Slick harness is set up for shielded plugs, so at least four REM40E shielded plugs will be required.

Moving up the cost scale, the Slick K4335 single impulse mag/gear combo and half harness would work.  Also requires shielded plugs.

The Full Monty is the Slick K4334-40 which is two impulse mags, complete ignition harness, spark plugs, gears.  This set up will solve all mag issues and make your engine start very easily.

A Bendix alternative is a set of 20 series mags and harness, but the cost will exceed that of the Slicks by at least 50%.

Harry

[RJW Note:  Another poster recommended El Reno Aviation, 1-800-521-0333]


A65 Quits on Roll-Out

Has anyone had the following engine problems?  On roll out the engine quits. A-65-8, with Eiseman mags---rebuilt, seems to be good rebuild and will throw 3/8" blue spark on bench.
Carburetor is a Stromberg Nas3- it was rebuilt buy a carb shop. since then, we have had it apart and checked float level. all passages are clean, jets are the right size, and visually it seems like it is good. It has a plastic needle and new seat, We also tried a steel needle and new seat. All AD's and notes have been complied with on this carb.

We have idle set to 550 to 600. after landing in three point roll out the engine will quit nearly every time. engine will quit when taxiing in, if idle speed gets too low.

We try to keep it 800 or above to keep from dying, Plugs are wet and it seems to be a low rpm mixture problem. once it decides to die, it is just like you turn off the mags switch. It can't be caught and brought back. When you go to start it, without touching anything, it will catch on the third blade and run real good for a few minutes like nothing ever happened, then die unless you keep it reved up a little. Black smoke will puff out at the lower rpm's when you throttle it up. This indicates excess richness at idle setting and the wet plugs do too. when we lean the idle mixture to stop the black smoke, it will pop indicating too lean of an idle mixture.

Static runs are good, no missing and it turns about 2100 to 2200. Mag checks are good, maybe 25 or so drop on both mags. I would call it good.

In the air at cruise, it is just great. When first starting here in the midwest at this time of year, it is very cold natured. Maybe have to start it two or three times to get it going and keeping it going. We have been running av-gas, premium car gas, and non alcohol regular. seems like the same thing with any of the fuels.

We also get small fuel drips at shut down for a couple of minutes. This doesnt seem bad, but I know that all 65 hp dont drip like this and I feel there is a relationship between the drips and the richness.

To set up the idle on the Stromberg carb it is a procedure of balancing the idle mixture and the idle speed set screws.  The idle mixture is a slotted thumbscrew half the size of a dime located at the top of the carb body facing aft.  The idle speed mixture is a small set screw on the arm that the throttle cable attaches to.  The idle speed can be set just using the idle set screw, but the mixture may be wrong and the engine can run too lean or too rich at idle, resulting in the propeller stopping.

The set up procedure will require that the engine be started and stopped several times.  Don't attempt to set the idle with the engine running! Invariably, you will be coached by some guy who will insist that the idle be set with the engine running, but the danger of working around a spinning prop is too great.

The first step in the procedure:  Does your tachometer read correctly?  It is not unusual for 60 year old tachs to read incorrectly at idle.  I use an optical tach made by Cermark, a manufacturer of model airplanes and parts. This optical tach runs $50 or so, but it is a very useful special tool to keep in your toolbox.

The engine idle should be 550 to 650 rpm.  Veteran Cub owners will suggest that idle be run down as low as 350 rpm.  This was possible with non-impulse coupled Bendix SF series mags, but too low for any impulse coupled magneto. If it is too low then the impulse couplings on the mags will engage and the engine may quit at idle and the oil pressure may be too low.  If it is too high, the airplane will probably run you down on start up.   The idle may need to be set 50 rpm high due to the low inertia of the wood prop.  Metal props have more weight, therefore more inertia, so may need a bit less idle.

Start the engine and observe the idle.  Gently run the throttle back and forth to find the idle position of the throttle.  There is a bit of "springback" in the throttle control rod and cable, which can affect idle. The throttle should always be positioned so that the stop is the set screw on the carb body, not the contact of the throttle against the airframe.  You may have to adjust the throttle linkage so that there is a bit of rearward clearance between the throttle arm and the airframe.

Next, using the idle speed screw on the throttle arm, adjust the idle to spec.  Start the engine and run the throttle back and forth a half dozen times to make sure that the linkage springback is correct and not interfering with the idle stop.

Now the tricky part:  setting the idle mixture.  This is simple to do with carbs with a mixture control.  When the mixture is pulled to idle, the rpm should rise about 50 rpm just before the engine dies.  The A65 is killed via the ignition switch, so it is difficult if not impossible to see any rise in rpm as the engine leans out and quits.  Setting up the A65 idle mixture is often done by ear.  Run the engine, lean the idle mixture.  If the engine backfires when the throttle is rapidly cut, then the mixture is too lean and needs to made rich.

Ok, that's the theory; let's consider your specific situation.  There are some idle bleed holes in the carb that may be plugged or obstructed that cause your engine to die at idle.  Does the engine stumble when the throttle is rapidly advanced?  If yes, then the idle bleed holes may be obstructed. Related to this is a loose throttle shaft to carb body fit.  If excessive air leaks around the throttle shaft, the mixture will lean out excessively and the engine will stumble at acceleration and die at idle.

Disconnect the primer line at the spider and cap it off with a little rubber cap.  The rubber caps are commonly used on automotive vacuum systems and can be bought at an auto parts store.  Vacuum in the induction system can pull fuel through a leaky primer.  The fuel from a leaky primer is burned up at cruise, but is very noticeable at idle and can foul plugs quickly.

Is the carb heat adjusted correctly?  A loose or partially open flapper valve will make the engine run rich at idle and foul the plugs.

How does the engine run without the air filter?  If the filter is restricted, then the engine will run rich and choke from lack of air.

On to the mags:  You mention that the mag makes a blue spark.  Was this checked simply by spinning it or on a test bench with a tach?  It makes a difference.  A mag with a bad coil may make a good spark at mid to high rpms, but won't make a spark at low rpm.  In short, the mag makes more energy the faster the magnetic rotor shaft is spun, so the more energy, the greater the chance that the generated spark can overcome an open or fault in the coil.  Your mags may simply be breaking down at low rpm.  On the bench, you spin the mag until it makes a spark, and it is possible to spin the mag 1000 rpm or so by hand when twisting it quickly.  A test bench is more accurate in that you can gauge the "coming in" speed, or the lowest speed at which the magneto will reliably generate a spark.

Another long shot is park plugs.  The old C26 series, REM40E, REM38 and REM37BY are all good part numbers.  Some of the early Unison Autolite plugs suffered resistor failures which would result in fouling.  Unison changed the design when the problem occurred and very few of the affected plugs made it into service.  I'm guessing that you are not using those, but if you are, let me know and I can give you more info.

I'm thinking that your primer is leaking or that your tach is not reading accurately when you are using it as reference to set up low idle.  Another possibility is that you have A75 metering jets in an A65 carb (although you mention that jet size was checked).  The mags may be at fault, but it is unlikely that both would fail identically at the same time.  Overall, you clearly have too much fuel based upon the black smoke and wet plugs.

Keep me informed of your progress and I'll do what I can to help out.

Harry

[RJW Note:  For more information on Stromberg Carburetors, see the Main Engine Page.]


Battery Charging Using an Aircraft Magneto

I've been daydreaming of ways to charge a small battery, and have considered solar panels (don't work in the hangar) and wind generators (expensive, heavy, draggy). An old-timer suggested that I  should consider taking power from the primary side of one of my mags  (already fitted so free and no extra weight). The mags (fitted to an A65) are TCM factory overhauled units and have done about 200 hours so far, so they are in good shape. I'd ideally like to charge a 12v battery at about 1 amp if I can get this much current without compromising the HT output of the mag. Has anybody tried this before?
In short, it is impossible to charge a battery using a magneto.  Here's a short list of why it won't work:

The primary output runs about 50-250 volts and is totally unregulated.

The output is an asymetrical DC, which means the polarity is constantly switching positive to negative to positive, etc.

Any power tapped from the primary circuit degrades the overall output of the magneto.  The magneto can only produce so much power, typically just enough to perform ignition functions.

It is generally unwise to tap into the primary lead of the mag.  If the secondary device fails, it can short out the mag.

I worked for Slick magneto for nearly 20 years and we experimented with a number of different magneto powered devices, none of which worked.  We did come up with a multipurpose ignition/generator,  which, ironically, looked like a generator.

I'm not an expert on lawn tractor ignitions, but I'm going to guess that the output voltage and pulse is different than an aircraft magneto.  There is some basic similarity between lawnmower, motorcycle and aircraft ignitions, but the components and technology are not always transferable from one application to another.

Another problem with any tap off of the magneto p-lead is that balance of the internal electrical circuit can be affected.  For example, there is an inline p-lead capacitor sold that is supposed to quiet noise emitted at the p-lead.  The problem is that the overall capacitance of the primary circuit is changed and the result is a longer duration spark at the contact points.   The longer duration spark results in more contact point erosion, which results in the points opening early, which results in weak magneto output.

P-lead tachs caused similar problems- I always noted more contact point and internal timing problems with magnetos used to drive p-lead type tachometers.

I find that a motorcycle battery with a quick disconnect to a trickle charger works the best.  Most motorcycle specific 2 amp trickle charges come with the quick disconnect connector.

Harry


Winterizing

First, my apologies: I am not flying a flybaby. I am flying a A65-8 powered Pietenpol, on skis.  I was wondering if you would have the dimensions of the winterkit plates use to restict airflow around the eyebrows baffles?  And also the plate that restricts the air intake. I know that there is a plate that goes in front of the carbheat box air filter because I remember seeing it on my brother's Cub around 1975. But that is 30 years ago.
I don't have any specific dimensions for cold weather block off plates.  Typically, the aircraft manufacturer determines the size of the block off plates.  I currently work for an airframe manufacturer and our scientific approach is to simply use duct tape to start blocking off airflow to obtain the heat rise required and then build a plate to match.

My suggestion is to start off with duct tape and progressively close down the inlets.  The carb does not get blocked off, but there is usually a hole in the cowling just above the carb which allows air to flow along the bottom of the engine where the sump and cam are positioned.  This hole usually gets a block off plate.

My experience, though, is that is is nearly impossible to get the oil temp much higher than 150F degrees during winter operations, especially with the open J-3 type cowling.  On 10F days I usually see only about 130F on the 7AC that I fly.

Harry


Lightweight Pistons for an A-80

I would like to find some lightweight 8 to 1 compression ratio pistons for my A-80 Continental on my FlyBaby as the stock five ring pistons are a real slug. I weighed one piston complete with wrist pin, pin buttons, and rings and it weighed 917 grams which is better than 2 pounds!
The piston weight that you throw out seems really high, but I don't have any A80 pistons on hand to evaluate.  I wouldn't be surprised, though.  The A80 was not a very popular engine and probably didn't perform so well due to the high reciprocating weight of the pistons.  I have noticed that the weight of various Continental pistons varies wildly as I have found some really heavy C85 pistons in my parts pile.

Usually I recommend Lycon for parts, but the guy I have worked with in the past has been away on leave for quite some time and I have noticed a change to the business.  I have also recently been told of pistons made by a company called Venolio, but I haven't researched these parts yet.
 

Harry


STC'ing a C-85 Piston in an O-200

I am an A&P/IA.  I own a Cessna 150L w/ O-200A, and want to install the C-85 Pistons in my O-200 and port/polish the intake and exhaust ports.  I want to do this under a program to produce an STC.  Any words of advise or ideas would be appreciated.  Is this a doable endevour??
STC projects are a fairly big project, especially for a project which will affect engine performance.  Typically, some sort of calibrated dynamometer will be required to obtain baseline data and to measure the enhanced performance.  Typical parameters which the FAA will want to document is horsepower, torque, CHT, EGT, and then calculations for torsional load on the engine.  All of the data will require an engineering plan along with the supporting documentation.   Overall, a pretty big project.  When I was at Unison, our LASAR ignition project probably involved 4 engineers full time, plus other marketing and manufacturing people for nearly a year.

However, nothing is impossible as I am currently working for a company which certified an airplane to the latest FAA standards (something Cessna, Piper, Beech, Mooney and Cirrus can't do).  The two guys who started this project were just a couple of A&P homebuilders with an idea and simply dogged their way through the process.

I would suggest that you contact your local FAA engineering office to get some info on how to pursue an STC.  I'm not sure if there is an advisory circular, but there is probably some sort of guidance in print from which you can work.

Harry

[RJW Note:  This process ONLY applies to engines on certified airplanes, like the questioner's Cessna 150.  You do not need an STC for a homebuilt.]


Rocker Arm Bushings and Low Oil Pressure

I have a homebuilt Super Emeraude with an O-200. The engine is "bottom" overhauled with new bearings and new hydraulic lifters. The aircraft has not been flown yet. Have just started taxi tests. My plan is to buy new cylinders when the aircraft has been flown, so the Cylinders can be run in properly in the air.
I have been struggling to get acceptable oil Pressure when the engine is hot. I am running the engine on 80 straight oil with oil Pressure  40+ psi up to 170 - 180 degrees Fahrenheit, but when the engine oil gets hotter the Oil pressure is falling. At 200 - 210 Fahrenheit the oil pressure is starting to fall slightly below  30 psi. The cylinders has (very) worn rocker arm bushings (especially the exhaust arms), and both inlet and exhaust arms have drilled holes for valve lubrication. The engine and  cylinders is produced by Rolls-Royce and has total 3200 hours since new. The cylinders has gone about 1200 hours since overhaul.

I know the oil is flowing through the cam followers via the pushrods to the rocker arms. As I understand from the TCM manual only the exhaust rocker arm should have the drilled hole for valve lubrication.

How much do you think worn rocker arm bushings is contributing to the low oil pressure? Do you have any comments about drilled rocker arm for the inlet valves ?

I don't think that the rocker arm bushings would result in low oil pressure. The oil pressure supplied to the rocker arms is a fairly low demand on the system.  The main bearings account for most of the oil pressure demand.

Typically, low oil pressure is the result of excessive main bearing or connecting rod bearing clearance.  Another source of low oil pressure is a worn or leaking oil pump.  Symptoms of either problem would be low oil pressure and high oil temps.

The new bearings may be aggravating low oil pump pressure.  With new bearings, the demand on the pump increases.  A weak pump may be able to pump oil through worn bearings, but may not be able to pump through new bearings. Another idea is that the crankshaft may be ground .010 under and standard size bearings may be installed.  If this is the case, then the clearances between then bearing and crankshaft journal would be too great.

It shouldn't cause a problem to have both rockers drilled for oil cooling, and I have seen engines from the factory configured this way.  It is a very important to have the rocker with the oil squirt hole positioned on the exhaust valve.

Overall, I'm leaning towards the oil pump is worn and not able to produce enough pressure to meet the demand produced by the new bearings.

Harry


Upgrading the Stromberg Carburetor for 75 HP

I have a A65-8 continental in my Fisher Classic, I would like to know what different sized venturi, jet, and bleed tube to change to for the Stromberg NA-S3A1 carburator to increase to 75 hp. I have already retimed the mags for 29 and 32 degres spit timing. this gave me 150 more rpm during full static engine run.
The venturi for the A75 is 1 5/16".  Main metering jet is a #46 hole and the main airbleed needs to be a #60 hole.  The specs for the carb are in the C75-O200 overhaul manual, not the A65-A75 manual.

Harry


C-90 Piston Upgrades

I want to get more hp out of my Continental C90 (experimental) and heard that an easy way would be to put C85 pistons in. Is that true and if it is, what will it do to the engine and its reliability. Would it be safe to fly it? Have people succesfully done it? Is there another way to increase power in a C90?
I'm starting to get to the point of describing power mods on small Continentals in terms of rpm, as opposed to horsepower.  For any given horsepower, the more rpms turned means that torque is being produced more efficiently.  Torque is king when turning a prop, and raw horsepower ratings may not accurately reflect an engine's ability to turn a prop of a particular diameter.  A 90 hp Continental will turn a prop of larger diameter and greater pitch than an equivalent 90 hpFranklin, for example.

The C85 piston has a bit more crown which results in a bit more compression ratio, something like 8.2:1 from 7.8:1.  Increasing compression ration is an easy way to get a bit more power and, since the C85 piston will drop right in, why not?  The added power is probably on the order of 8 horsepower or so and does not strain the engine.  The piston change is not certified, so it is only good for experimental engines where the data plate is removed from a certified engine.

Unless you want to get really wild and spend a lot of money, the piston change is the easiest way to add some power.  Dynamically balancing the reciprocating parts will add maybe 100-200 static rpm, which means that power available is generating torque more efficiently.  Bumping the timing from 28 to 30-32 degrees will also add some power, but also drive up the CHT.  Polishing the intake and exhaust ports can add a couple of hundred rpm, but is labor intensive and kind of expensive- about $2K for a 4 cyl engine.

There are a number of performance mod variations, and none are exactly the same.  But, many different mods yield equivalent results.  The problem is,
that you almost have to do all of the big, expensive mods to see big improvements- just picking or choosing a bit here and there may not provide
any significant results.  The piston change is one that is easy and gives a noticeable result with little added effort or extra money.

The easiest way to notice more performance with a small Continental is to lighten the airframe it is pulling- lighter airframes stall slower, take off faster, climb better, cruise faster.  In most cases, adding horsepower only improves rate of climb, but not much in speed.  Speed gains are usually drag, rigging and weight issues.

Harry


Case Magnetos

Do you know there to find timing and parts info and part the Case  Mags?  Would the gears from the Case fit a bendix SL4 .
New parts for Case magnetos are non-existent.  I worked for Slick for nearly 20 years, and our company origin was the Case magneto line.  The only parts available are those that have been salvaged and reworked from nearly 60 year parts.  There may be some parts that some of the companies below make for tractor use, but the tractor magneto was substantially different than the aircraft Case magneto.

Operationally, on a good day, there were a couple of problems with the Case mags.  The carbon contact was a part of the coil, as opposed to the block and would shake during operation.  The result was carbon dust would be dumped in the mag and the engine would periodically run rough, usually under load at takeoff.  The impulse coupling was a tightly wound piece of spring wire and never really worked all that well. 

The gear from the Case magneto and the Bendix impulsed coupled magneto are not interchangeable.  The Case gear was riveted to the coupling and the offset is different than the Bendix.  The net result is that the dimensional stack up is different between the two mags.  The direct drive gear from the non-impulsed Bendix SF series and Case mags are interchangeable, but both mags are difficult to repair and maintain due to lack of new spares. 

The best conversion is the Slick K4330-40 which includes two impulse mags, new drive gears, shielded harness and shielded spark plugs.  This kit absolutely cures all starting, reliability and parts supply issues, but is expensive- maybe like $1400 or $1600USD. 

There is a non-impulse magneto which is available, the Slick 4302- $450USD or so.  If you are really on a tight budget, you could install one of these and use the two Case mags to build up one good one.  You will need a special direct drive gear, but I could sell you one for $50.  This is not my favorite way to go, but if you are really trying to do it on the cheap, this method at least provides for one new, reliable magneto. 

My opinion, based upon 20 years of looking at every broken magneto combination possible, I would not use the Case magneto (unless your goal is 100% historical accuracy).  There are veteran experts who will tell you that the Case mag isn't so bad, but their point of reference probably originates from when the Case was a new mag 50-60 years ago.  I have no vested commercial interest with Slick or Bendix, but, knowing what I know, I simply would not mess with antique magnetos for a daily flyer. 

Harry 


Mechanical Fuel Pump on an O-200

Can I put a mechanical fuel pump on my carburated Continental. O-200 as on the C85 ,I don't like to rely only on an electrical pump on my new SE-5A biplane.
The O200 can be set up for a fuel pump, but it is a lot of work if the case is not machined to accept the pump.  On the right front side of the O200 there is a boss to mount a fuel pump.  If it is not machined, it will need be surfaced, a hole cut for the fuel pump arm, and holes drilled for the studs.  You will also need a special cam with an eccentric to run the fuel pump lever.  There are no drawings outside of the factory, and TCM is not going to share the info.  You can copy the dimensions from a C85 set up for a fuel pump.  Overall, a lot of work. 

Your SE-5A replica should not require a fuel pump. Your C85 might have been salvaged from an Ercoupe, and the fuel pump kind of came along fro the ride.  I fly a Cassutt which does not have a fuel pump and the head pressure is likely less and the demand greater than your SE-5A. I've never had a problem with fuel delivery.  Typically, as long as there is a foot or so drop from the tank to the carb, a fuel pump should not be required. 

Harry 


Finding Carburetor Parts

I am looking for a Stromberg NAS-3 or a Marvell MA3SPA carburetor.

Contact Greg Dart in Mayville, NY- 716-753-2160 or 716-753-3553.  Greg usually has a good supply of Continental parts on hand.  Otherwise, carbs pop up on Ebay on a pretty regular basis. 

Another idea- you might want to join the Aeronca Fliers discussion group at yahoogroups and ask around about a carb- that tends to be a fairly active group. 

Harry 


On Mag Drop

I am getting ready to fly N6318 and I have been doing a lot of driving around the airport getting comfortable. I have a problem on the Left (lower plugs) magneto. I drops on average 125 RPM. The A-65 Continental manual says "75 RPM maximum" drop and the Right (upper) magneto has no problem staying within this limit. The manual was written with Eisemann magnetos however and I am running Slicks with a Slick harness. I was running pure 100LL and now switched to 50-50 100LL and autogas to try to "get the lead out". Right after I cleaned the lower plugs it dropped 50 RPM but returned to dropping 125 RPM within 5 minutes of running time on the new fuel mixture. Other than some oil residue coating the lower plugs, I could not find any lead fouling at the cleaning. I do not have a mixture control on my engine.
So, how abnormal is this?

It is not unusual for the mag firing the bottom plugs to have a higher rpm drop than the mag firing the upper plugs.  In fact, some Continental engines stagger the timing so that one mag fires a bit before the other, just to even out the mag drop.  Another way to even up mag drop is to set up the ignition harness to cross over so that each mag fires a set of top plugs and a set of bottom plugs. 

As a rule of thumb, the split between the left and right mag drops should not exceed 50% of each other.  In other words, if one mag drops 75 rpm, then the max for the other one should not exceed 150 rpm.  It is nearly impossible to achieve perfectly even mag drops, so some variance is normal. 

I am out on the road right now, so I don't have a manual available, so I can't confirm the 75 RPM max for the A65.  It seems low to me, though.  I would think that a 125 to 150 rpm max would be reasonable, with no more than a 75 rpm split between the two mags. 

Something to consider is the quality of the mag drop.  Does the engine run rough on one mag versus the other?  If it is significantly rougher on one mag, suspect a mechanical problem with that mag.  Will the engine turn rated static rpm?  Will it turn static rpm on just one mag or the other?  It should.  Ultimately, the purpose of the mag check is twofold- to find a problem prior to takeoff and to determine if the engine can be run safely on one mag. 

Troubleshooting this problem is pretty basic- check the timing of the mags to the engine, rotate the bottom plugs to the top, etc.  Both mags should be identical on this engine, so swap the mags left to right and see if the problem moves.  The single most common problem that I encountered over nearly 20 years of troubleshooting mag problems while working for Slick was mistimed mags.  And of mistimed mags, the leading problem was incorrect insertion of the timing pin used to align the magneto to the engine firing point.  Usually, removing the mags and swapping from side to side fixes any problems with incorrect engine to mag timing (it is unlikely that the same mistake in installation would occur twice). 

Both mags on your engine are right rotation and should be pinned for "R" or right rotation.  Given that your problem is with the left mag, there is a high probability that it was mistakenly timed for "L" or left rotation.  The left mag should be timed for "R".  In short, time the mags for rotation, not positioning on the engine. 

You may have attached a timing light to check the points and confirmed that the points are opening at the correct firing point.  The problem is, if the left mag was pinned wrong, the points can be synchronized properly, but the distributor gear is not positioned correctly and firing one tower off.  The engine may run, but the result may be a high mag drop. 

I would highly recommend re-timing the mags.  If this doesn't solve your problem, just e-mail me back and there are a number of other areas I can suggest for troubleshooting. 

Harry 


Modifications for Maximum Performance

I saw some comments on a website that had you discussing some modifications to a C-85 that you were in the process of performing. I have purchased a midget mustang airframe damaged in a landing accident. I'm starting the rebuild process. It did not come with an engine. I have purchased a run out o200 and will go through it. Being an experimental I'd like to pep up the engine performance.
I have an airflow performance mechanical fuel  injection unit and will fit it. I've looked at a Cassutt racer page where 2 newsletters have been posted http://cassutt.lornet.com/pages/link.htm dealing with o-200 mods. I've also read Ken Paser's book on installation tips.

I spoke to Ib Hasen at National Aero an he talked about doing the following.

I'd like to get an honest 125 to 130 hp at no more than 3000 rpm. What reliability and performance mods would you recommend?
The work described  is typical of the things done to build a full-on race O200.  Because so much machining work is required, the end result is pretty expensive.  Most of the modifications are to ensure that the engine will run in extreme race conditions at redline temps while turning 3800-4000 rpm or more.  Keep in mind, these engines don't run much more than 50-100 hours (or less) before being torn down for rebuild.  I have just torn town a highly modified engine which was built right and run at about 3400 rpm for most of its life.  It lasted about 200 hours before the main bearings were shot. 

A consideration with building a high performance engine is that you really need to do all of the mods to realize the full potential of the mods.  Just picking some of the mods may not provide any benefit.  In my opinion, however, there are some select bolt in and set up mods which will yield a solid 10, maybe 15 horsepower increase. 

Your Midget Mustang is only going to go so fast and will not be able to obtain the 250+ mph that the Formula 1 race planes achieve.  Frankly, airframe drag reduction and lightening may yield more results than more horsepower.  Even with a very clean airframe and 130 hp, you will probably see 180, maybe 190 at full throttle at altitudes lower than 5000 feet.  You might be able to get more, but the M1 is a bigger, heavier, draggier airplane than a typical Formula 1 racer.  The big benefit that higher horsepower will bring to you will be improved rate of climb and shorter takeoff as any extra thrust in a high drag regime will yield a greater net result. 

You might want to consider an engine which has improved performance but not all of the exotic and expensive mods.  The engine that Ib Hansen describes will cost about $25-$30K- unless you have access to unlimited machine shop services and a donor for some of the exotic coating processes. 

However, there are some fairly economical mods which can yield tangible benefits.  First, up the compression ratio.  The standard CR is 7.8:1 and upping it to 9.5:1 is a quick and easy mod.  LyCon sells NFS pistons for about $800 set, http://www.lycon.com/ .  Klaus at Lightspeed also sells pistons, http://www.lightspeedengineering.com/ .  A slightly less expensive piston mod is to use a C85 piston in the O200.  The C85 piston has a bit more crown than the 0200 and your can pick up and easy 8-10 hp. 

However, by the time you have purchased and modified a set of C85 pistons, you are in the price range of the special NFS pistons.  Keep in mind that Ib suggests C85 pistons because the specs for Formula 1 racing engines calls out for specific parts, compression ratios and swept volumes.  If you are not building a Formula 1 race engine, you have many more options 

Balancing the crank, rods and pistons is a good mod, but expect to pay about $1000- $1500 for this service.  Balancing, in effect, lets the crank spin easier with less resultant stress and helps preserve the bearings.  If you run any type of prop extension, the crank flange needs to be absolutely flat- no plating whatsoever.  A really good prop extension will run about $1000 for a 10"-12".  Keep in mind, the longer the prop extension, the greater the leverage and torsional stresses on the bearings.  A 6" to 8" prop extension will work with the least amount of relative ill effects, but the torsional stresses really pile up above 10". 

Bumping the ignition timing from 28 to 30-32 degrees is also good for a couple of easy horsepower.  When setting up the mags, the internal cam may need to be profiled to ensure that the spark is symmetrical from lobe to lobe.  The Slick mags usually have a "cam spread" of a few degrees.  For example the mag is set t fire at 28 degrees on cylinder #1, but when the crank is turned to fire the next cylinder, the timing may be at 25 or 33 due to the unequal lift of the cam.  Sanding the Slick cam to make it lift evenly will really smooth out the engine.  An aftermarket electronic ignition, like Klaus' at Lightspeed will yield some benefits at altitude. 

The stock cam actually works pretty well up through 3200 rpm, but will definitely need to be re-indexed above 3400 rpm.  There are probably some exotic cams available, but, given the relative bang for buck ratio, it is hard to beat a stock cam.  I think that the C90 cam has a slightly different profile which may give a bit more torque.  There is a slight difference between an original 1940's C90 cam and the O200 cam.  I think that TCM may now sell the O200 cam as a replacement for the C90.  At one point in the past, the C90 was optimized to drive a wood prop, and due to the thickness of the prop, a bit more torque was required. 

All of the other fancy stuff like ceramic coatings helps, but is pretty expensive and exotic for the typical daily flyer.  Wrapping the induction tubes to ward off heat is a pretty easy mod, but not really needed if you don't expect to run your engine at more than 450F.  Porting and polishing works, but is pretty expensive considering that the ports typically require cleaning and re-polishing after 100 hours or so to remove the normal accumulation of combustion byproducts.  Polishing of the reciprocating parts relieves surface stress and helps with oil drain back into the sump to help carry heat out of the engine.  Once again, kind of extravagant if the engine is not run much beyond 3200 rpm and never seems temps higher than 450F. 

Here's my recommendation for a strong, bolt together daily runner engine: 

The piston, balancing and accessory case mods will add about $3000 to the basic overhaul of your engine.  A lot of the little things like bearing hole matching can be done with a file on the bench.   In general, use as many new parts as possible. 
Klaus Savier at Lightspeed Engineering has been running a high output O200 for many years and is also a very good source for information on hopping up the O200 and long term reliability.  The Formula 1 hop up methods really aren't designed for longevity, but more for burst of maximum power for a relatively short period.  Both Klaus and the Formula one guys will advocate lots of mods, but I feel that 90% of the potential power increase can be realized by my recommendations above. 

Harry 


Piston Ring Installation Orientation

I'm rebuilding an A-65 with parts purchased from Fresno Airparts.  The book says to install the rings with the part number of the word "top" towards the top of the piston.  Naturally, my rings have no part number or words on them.  Only a dot on the side with a 45 degree bevel on them.  May I safely presume this is the top of the ring?
The 45 degree bevel is oriented towards the top of the piston, and the dot or part number is usually embossed on that side. 

Harry 


Oil Pressure Dropping in Flight on New Engine

First things first.  Many thanks to you for offering your insight on the small Continentals.  Your information has been incredibly valuable to me while switching from a Rotax to a newly 0-timed A-75-8.  Since I've got 20 years flying on 2-strokes and 20 minutes flying on my A-75, your knowledge is a godsend!
I experienced a problem when I recently flew my airplane for the first time on the new engine. Things were apparently going well until I noticed the oil pressure starting to drop steadily.  On the ground, prior to flight, the oil pressure showed a little over 20 psi at about 800 - 1400 rpm.  A few minutes into the flight I noticed the pressure slowly backing off from about 25 psi or so.  I landed within 5 minutes as the pressure dropped more rapidly.  I shut down and started looking for oil leaks, but found none (I will do a more comprehensive check behind the panel).  I started up again and noted that I was now not getting any oil pressure at all, so I quickly shut down. One other note is that my oil temperature barey broke 135F the entire time I was flying.  CHT was good at 325 - 350 and steady.

When I first ground-ran the engine after the re-build I got no oil pressure, so I removed the screen and poured some oil in to prime the pump.  Then I got 20+ psi on start-up after that.  My oil lines aft of the firewall are small copper lines about 1/16th ID.

I'd be grateful for your opinion.  Is it a bad guage?  A a blocked line? Could the copper lines be too small?  Since I have zero experience with these engines I'm at a loss.

The condition that you describe sounds like a classic four cylinder Continental oil pump problem.  The A-65 is particularly prone to this problem.  Basically, there is either too much edge clearance between the oil pump gear teeth and the walls of the oil pump pocket in the accessory case, the holes where the oil pump gear shafts pass through the accessory case are worn, or the depth of the oil pump pocket from the base of the well to the top of the cover plate is too great and oil is leaking past.  It could be a combination of all three problems.  Another remote possibility is that the oil pressure relief valve and valve seat are worn. 

The pump can lose pressure and be re-primed to get things back to normal. However, this should not be a regular occurrence.  If you have to re-prime after every flight, then there is a problem with the oil pressure system. 

The easiest part to check is the oil pressure relief valve.  There is a domed brass plug on the rear case under which a spring and piston with a tapered end are positioned.  The spring rarely goes bad, the tapered end of the piston should be uniform and free of steps or corrosion.  The mating seat that the tapered end of the seat contacts should also be uniform. Prior to assembly I fit a wooden dowel to the piston and lightly lap the mating surfaces of the two seats using valve lapping compound.  This can be done with the engine assembled and in service, but use a sparing amount of compound- a little bit goes a long way and it is pretty abrasive.  You want to be really careful as the compound is very abrasive and too much can enter the oil system of the engine and cause problems.  I'm going to be honest, this solves maybe 2% of the problems. 

Which leads me to the most likely route to fix your problem.  The accessory case will need to be removed and the oil pump worked on.  Many times, just repositioning and re-torqueing the oil pump cover plate will work.  I also like to lap the plate surface (if the plate is used).  You need a dead flat surface to do this- apply a film of valve lapping compound on the flat surface and lightly rub the plate over it in an orbital motion.  Re-working or re-positioning the oil pump plate works 25% of the time. 

More than likely, the oil pump cavity and the shaft holes are out of tolerance.  The only repair is to send the case off or search for a better accessory case.  Unfortunately, due to the fact that the case is magnesium, it is tricky to repair- about 50% can't be repaired and the case gets destroyed during an attempted repair process if it doesn't work out.  Drake Airmotive out of Tulsa can do these types of repairs. 

One of the guys on the Fly Baby list has conjured up a sleeve for the oil pump pockets, but the repair is not approved.  Drew Fidoe is a Canadian from BC, but he is on a military tour in the Persian Gulf and won't be back into Canada until October/November.  I will see if I have any technical notes on his repair. 

One way or another, you will have to take the accessory case off of the engine to do troubleshooting and repair.  This is a real pain, but there are no shortcuts.  However, working on the Continental oil pump is like heart surgery, so I encourage you to seek other opinions.  You might want to go to the Yahoo site and sign up for the Luscombe, Aeronca Aviators, and Cub chat groups to see what kind of experience you may find there.  There are several good contributors to both the Luscombe and Aeronca groups. 

You will probably get one bit of advice that never seems to work out.  There is the idea that putting small washers under the oil pressure relief spring will help.  Well, if your pump isn't making pressure, it isn't going to help. The stock combination of parts should provide for adequate and correct oil pressure. 

One final thing- you mentioned low oil temp.  This is probably due to no oil flow or pressure.  If the oil doesn't flow around the engine, then it won't pick up heat generated by the engine. 

Let me know how things work out and keep in contact if you have more questions. 

Harry 


Crankshaft Part Number

I am taking an A-65-8 apart to overhaul. The crank has a A5334 on it. I can not find that number in any of my books. Can you tell me something about that crank?
It is a taper shaft with 4 holes in the hub lock. It looks very good and is ten thou under.

Any help would be welcome.

I'm out on an extended trip for the next three weeks, so I'm not near any of my parts.  But, I think that the number you are looking at is the casting number, or maybe an early part number not reflected in later parts manuals. There are no bogus taper cranks for the A-65, so I'm pretty sure that the crank you have is correct for the engine. 

The only thing to check on the taper crank is the keyway slot for cracks.  This is a very common problem with the taper cranks. 

Harry 


A65 Crankshaft End Play

I have a question for you about the A65 continental.  How much end play is acceptable for the crankshaft (fore/aft movement of the propeller hub)?
.004 - .015 is new limits and max service is .025. 

Harry 


Engine Not Producing Full Power

I have a 1946 7EC Aeronca Champion.  Recently, the C90-12F Engine was overhauled, and now the engine won't produce minimum RPM with a standard propeller.  My local A&P that installed the engine for me is baffled.  The overhaul shop tells me it ran up fine on their dynometer.  Is is possible they installed the wrong cam or carb?  The airplane actually performed better with the blown engine.  Could they have put 0200 parts in my C 90 or are the parts all the same?
I really appreciate any advise you can give me.  It seems no one knows about these older engines any more.

First off, it is unlikely that the engine was assembled wrong.  It can happen, but the problem that you describe is not unusual and is usually related to installation set up.  The single most common problem right after overhaul for lack of RPM is usually the throttle linkage set up. 

The C-90 and O-200 are nearly identical, parts-wise.  The pistons and crank are the same, and the cam differences are small. 
Let me know how things work out and I'll continue to help you along. 

Harry 


Radio Noise from Unshielded Ignition

I have a Piper PA-11 with a factory original C90-8F engine.  I want to use a hand held radio but the electrical interference renders the squelch inoperative.  I know that I could use a shielded ignition harness but  that would mean that I would need to install cowling bumps on the top cowl.  I don't want to do that.I currently have a shielded harness installed with shielded plugs on the bottom.  The 4 top plugs are the original "automobile" type ceramic plugs.  In the course of my research, I came across a picture of a shielded cover that went over the ceramic plug and to which a shielded harness could be attached.  Do you have any idea where I could get information about these.  Do you have any other suggestions that would solve my radio problem?
Fresno Airparts sometimes has the little add on "cans" which shield the old style spark plugs- 559-237-4863.  I also seem to remember some guy who was building these cans new, but I will have to do some research.  I can't get to that for a couple of days, but I will let you know if I find anything. 

Another thing I've done is to use shielded plugs on the bottom set and simply turn off the unshielded set during heavy ATC communication. 

Other than that, unshielded plugs are just what they are.  There is no current manufacture plug which will provide shielded operation and fit in the stock PA-11 cowl. 

Here are some links which may be helpful 

Why Tolerate Radio Noise?  from the EAA Members web site. 

The Taylorcraft Infor web site has pictures of the shielding cups.  Here's an exerpt from the site: 

The BC12-D uses unshielded plugs and wires.  To improve radio reception it is desirable to replace these with shielded wires and plugs.  Modern shielded plugs and wires are significantly taller than the original, and for the top plugs require a bump outs rework to the original engine cowling. One idea is to use shielded plugs and wires only on the bottom set, and switch the magneto to this set during radio conversations.  Another suggested alternative is to use Ercoupe Cups available form Fresno  Airparts (559-237-4863) for $16.50 each.  You have to turn the threads down to fit the standard shielded plug harness end.
Fresno is mentioned numerous times in various other sites for the shielding cans.  Another possibility is Skyport Services 800-624-5312 or Univair 800 433-5443.  The cans seem to be an Ercoupe part and both of these companies sell a bunch of those parts. 
Harry 

[The original poster sent a follow-up] 

I  just called Fresno Airparts and they do have the cups in stock.  They  tell me that the tube on the side of the can is currently tapped for 11/16 X 24 thread (an old harness specification.  To make them work on a current  harness, all that needs to be done is to retap to 5/8 X 24.  The standard shielded harness will then fit like a glove.


Timing Magnetos

Sorry to bother you, but having trouble seting the timing on my two slick impulse mags on my O-200 powered SE-5a. 
I'm using one of these" tweeter"timers... 

As I understand,the points should open 24 degrees before TDC and then the impulse coupler snaps at TDC.  If I rotate the prop untill the impulse snaps at TDC, then the points should be timed at the correct 24 before TDC,or should I ignore impulse and simply rotate prop untill points open?  It seems so simple but ,but I have no experience and can not find anyone who has any, to explain it . Thank you for your time 

Here is the procedure: 

Let me know if you need more info. 
Harry 

O-200 Crankshafts

I have just found your wonderful web page.THANKS!  Do you know where I can pick up an 0-200 crank  as a bargain for my experimental?
Thanks for the comments on the page- I'm a somewhat reluctant recruit in that  I don't consider myself a total expert, but I'm happy that the information that I've put out there seems to be useful. 

The O-200 crank has a service limit to grind of .010 under, which means that there should be a good supply of used ones that won't make the cut.  There are bearings for the A-65 engine which are designed for a .020 grind.  Now, the A-65 bearings are not legally approved, but should work with the O-200 crank. 

Here's the rub, the bearings and grind job will probably cost nearly as much as a new O-200 crank.  Automotive shops can't do the grind properly because
the radius between the crank and the journal is different than automotive applications.  Most auto shops don't have the right tooling.  Another problem is that the O-200 crank is nitrided for hardness and the grind has to allow for a slight dimensional increase for this process, and most automotive shops aren't going to have the experience to do this process right..  The long and the short of it, it is highly advisable to send the crank to an aviation shop, but this will cost a few bucks. 

The best prices for new O-200 cranks seem to be found at Edgecumbe G&N, www.edgcumbegn.com 800-621-1319, Precision Aircraft Parts 800-932-2192, or Mattituck 800-624-6680.  G&N's price is $1850. 

However, I would suggest that you contact Aircraft Specialties in Tulsa to get a price on the .020 bearings and an experimental grind for a used O-200 crank.  They might have a used crank and probably have done this work before.  They might also tell you that I'm full of hat air and it can't be done, also!!  www.aircraft-specialties.com 800-826-9252.  One of the most experienced builders of experimental engines is Dick Waters at Air-Tec engines, 800-366-4746.  Dick has been in the game a long time and is a pretty reliable source of info on parts interchangeability, experimental grinds, bearing substitution, etc. 

Harry


A-80 Engines

I have been  considering building up my A-65 core with A-80 components (pistons & valves)  is this recomended or ?
You are probably better off building an A-75 than an A-80.  The biggest problem is that the A-80 pistons are very heavy- I mean really heavy.  The 75 pistons are much lighter and easier for the engine to swing, so probably yield the same net horsepower. 

Use a prop that turns a bit more rpm, like 2500-2600 versus the stock 2300 rpm for a bit more oomph. 

Harry


Continental Engine Overhaul Video

I bought a DVD off of Ebay which is a copy of an 1940's training film on overhauling an A-65.  The video quality is pretty good, a bit chattery at times as the old films were, and is narrated by the monotone voice that must have narrated a million instructional films through the 40's, 50's and 60's..  The video gives a pretty good summary of the teardown and inspection of an A-65, but is lacking in specific technical detail.  For example, there is a scene where the narrator talks about checking for cracks and the mechanic is shown looking around for cracks with a flashlight.  Cracks found with a flashlight are more like canyons than cracks!! 
The video is fun to watch, though, and on the cool factor, I rate it-  cool. Check out ebaymotors- I got mine for about $14.  By the way, I have also purchased copies of the various CDs with parts and overhaul information and they are all very good. 

Harry


Rusty Crankshaft

I have a very nice looking A-65/C-85 flanged crank with solid crank  throws that mikes and indicated perfect original dimentions.  The  problem is that there are many smallish rust pits in the nose seal  area. Can this area be ground undersize some(how much) and still have  a good seal?

A-65 cranks are pretty hard to find, so I save any cutting and grinding as a last resort.  Once the metal is gone, it is gone. 

A couple of different approaches on the oil seal area.  One is to polish the surface with emery and crocus cloth to make the surface as smooth as possible.  As long as the edges to the pits are relatively smooth, then the oil seal may work ok.  When polished the corroded area of the crank should appear as black stains in the shiny metal area which was polished.  If a fingernail still can be picked against the polished corrosion, then a grind is likely. 

Another approach is to install the oil seal only partially so that the edge of the seal is riding on a "new" or less worn surface of the crank. Basically, don't push the seal flush to the case, just leave it out about 1/4" to 3/8". 

There is a gamble with my approach- you may experience an oil leak and have to tear the engine down to fix it.  However, I consider my time and a gasket set to be fairly cheap. 

Just a suggestion if you want a recommendation on a shop to look at your crank.  Go to www.poplargroveairmotive.com.  This is a pretty nice engine shop close to me and they are very consumer oriented and have a knack for saving parts that may otherwise be scrapped.  They understand antique engines pretty well and would rather repair and save a part than immediately start grinding and cutting.  Ask to talk to Dave Allen and see what he has to say. 

Harry


Stub Stacks on A-65

I am going to put an overhaul on the A-65 this winter.  I don't like the Aeronca "snaggle tooth" stacks and was wondering what you all thought about stub stacks on the Flybaby.
There is a plus and minus to stub stacks on the A65.  First, there is no functional negative or positive to stub stacks- they are considered a "neutral" configuration.  Pretty much all engines are developed with straight stacks so that the exhaust has no negative or positive influence on engine performance. 

A couple of slight negatives, though.  I never really cared for the sound of short stacks.  Because of the placement of the stacks, the fuselage can block the exhaust noise for one side and the engine kind of sounds like it is missing.  However, the short stacks do have their own distinctive sound, so maybe it is not a big deal.  The very best sound can be had when all of the outlets are clustered together closely with individual outlets.  The RV6 uses this type of exhaust and it really sounds good. 

Another consideration is that a carb heat muff will need to be fabricated. One of the benefits to the Aeronca exhaust is that it is ready fit and little things like carb heat muffs are readily available. 

Other than the above, no real problems with straight stacks. 

Harry


Poor Hot-Starting Performance

I have a c-90 with a stromberg carb in a Luscombe 8F.
The engine starts cold on two shots of prime with the throttle just cracked. It idles well and runs up to full power and in cruise all is well. The carb
heater works fine and the mixture, well it's not that effective and should be wired open to keep it from creeping to the lean position. When I come in
to land with the engine hot, throttled back to 1500 RPM, the engine dies and will not start hot, with any throttle setting. Once it cools, it'll start
again. I've put in a new float and needle, all set to the book. Why will it not start hot?

It is possible that the dimensions of the throttle shaft and throttle shaft holes in the carb are too great.  If the fit of the shaft gets too sloppy, then air can be pulled into the carb and the mixture will go way too lean. The initial sign of a problem is a slight backfire when the throttle is retarded, which then becomes worse as the wear increases.  A too lean idle mixture will also cause the same problem. 

Plugged jets in the carb throat can also be a problem.  If the throttle stumbles on take off, I'd make sure that the jets are clear.  DO NOT use compressed air on an assembled carb- the sudden air pressure drop can collapse or damage the float. 

How about the mags?  The old Bendix SF4 mags are notorious are susceptible to getting hot and making the engine difficult to start.  You may have a layered problem- the carb dies at idle and non-impulse mags don't have the retarded spark delivery to start the engine easily. 

Harry


Vibration Problems

I had a soft cylinder (19/80) on my C85-12F and replaced it with a nominal overhauled unit, the bad cylinder was .020"+ over. With the new cylinder I now have excellent power but also a vibration that was not there previously. It can be felt through the rudder pedals at most of the rpm range and is visible as a cowling and side window vibration at anything above 1600-1700rpm. The cylinder shop advised that replacing an oversize cylinder/piston with a standard would not be an issue.
Is there any value in getting a dynamic prop balance or is it more likely a piston weight issue? The cylinder was making little to no power before the change (clean plugs and exhaust), so there is I presume a power pulse added to the system, not sure if this is a factor.  Theoretically, if you install an oversize piston and the jug makes more power relative to the other three, then there is the potential for an imbalanced power pulse.  Typically, oversize pistons don't are not usually noticeable during routine operation, but that is not an absolute conclusion. There could be some imbalance noted if the conditions stack up just right.

Dynamically balancing the prop may help as most vibration as you describe is prop related.  It could be that  you have had a low amplitude vibration of some sort all along, and when the cylinder was overhauled the vibration moved to a frequency which was more easily noticed. 

I currently have a slight vibration problem in my Champ.  All of the cylinders are within the leak down tolerance, but the high one is 80 and the low one is 65.  At last annual, all of the cylinders checked out at 78-80 and the engine didn't vibrate as much. 

Leaking primers are another culprit- if fuel seeps out then the engine will run just a bit rough.

Harry


Boring/Balancing an A-65

You mention that automotive engine shops might remove material from the wrong places when align boring and balancing an A-65.
Could you provide some guidelines that we can pass along to the machine shop to prevent this from happening?

What other tips might we pass along?

The biggest problem is the connecting rods- the weight of the Continental rods varies significantly from part to part and significantly from end to end.  The high performance aircraft engine shops literally keep boxes of rods on hand and match up from existing inventory to get four to six rods close in weight before balancing.  The chance of finding four rods within several grams of each other is pretty rare.  The big mistake is that too much material is usually removed from the piston pin end or the radius where the rod blends into  the pin or journal end.  The A-65 rod is pretty light in comparison to a Chevy 350 rod.  The A-65 rod is also manufactured to 1938 machining and material standards, and the density of the castings varies much more than modern automotive parts. 

As far as absolute standards go, I don't have any.  I usually send my parts off to companies like Barrett Performance or Lycon who have tested, or blown up, engines as they gained experience.  Lycon, in particular, does the job right.  They will pick from boxes of rods, and get stock parts which are very close in weight, and then just grind a bit from the molding flash on the centerline of the rod to get the weight in line. 

Harry


Lycoming O-145

Is there anything relatively easy and relatively inexpensive that can be done to improve the performance of the Lycoming O-145 engine on the Fly Baby? (Short of replacing it).
Unfortunately, not much you can do with the O-145- it is a pretty anemic 65 hp on a good day.  It is 145 cubic inches vs the 170 of the A-65, and cubic inches nearly almost always wins the torque battle.  About the best you can do is use a climb pitch prop and give up on some cruise speed.

Harry


Slick Mag Inspections

Harry, could you talk to us about the requirement for 5 year(?)/500 hour(?) magneto inspection(?)/overhaul(?)  Clearly I have lots of blank spots here, since I can't even frame the question without multiple question marks.
I just happen to have my slick mags off my A65 at the moment, and now would be a good time to do whatever is required to them.  I put them on in 1996, and they have about 800 hours on them.  I love these mags, and was somewhat distressed to hear from an A&P friend recently that there was some 5 year or 500 hour requirement that I had not met.

Here is the bottom line for Slick mags regarding inspections:  Slick recommends a 500 periodic internal inspection of the magneto.  There is no requirement for a five year inspection, nor is an internal inspection required by an FAA AD- two big misconceptions.  The bottom line is that a private owner can run magnetos with no inspections as the requirements, while considered mandatory by the manufacturer, are not enforced by FAA decree.  That is, unless there is a failure, at which point the FAA and insurance underwriters default to the manufacturer's recommendations and pin the blame of the failure on lack of maintenance.  The point is, ignoring manufacturer's recommendations are not a problem until there is a problem. 

Related to the above, while a non-commercial, private owner may elect not to adhere to the manufacturer's recommended schedule, the mechanic may have a different perspective.  Ultimately, the mechanic will have to put pen to paper to endorse that the aircraft is airworthy after leaving his hands.  To a large extent, adhering to the manufacturer's specs is a get out of jail free card for the mechanic.  Unless he botches the work, a mechanic will be largely covered if he can document that the work was done properly. However, he will be hung by the FAA just as fast if it is documented that he did not do the work. 

I have written volumes on this over the years, so a few sentences on the topic does not do it justice.  The bottom line is that it is just common sense to have your magnetos inspected on a periodic basis.  Mags tend to fail in a progressive manner, so the warning signs leading up to a hard failure may be subtle, or get lost over a long period of time.  The internal parts of the mag- points, cam, coil, and distributor block- are all subject to wear.  There comes a point where the parts wear and the mag becomes inefficient or mechanically and electrically stressed in that the mag has to work "harder" to make a spark.  A classic example is worn spark plugs:  A wider gap demands higher voltage, the high voltage means increased wear at the contact point face due to electrical erosion.  As the points wear, overall electrical demand increases on the coil, creating heat due to electrical generation.  The heat increases resistance in the coil and the need to increase the electrical push increase with the added resistance.  If all of the parts in the system are adjusted regularly, then the overall stress is balanced and parts last longer.  If the balance is not maintained, then parts work harder, decreasing the reliability gap. 

There is an argument to be made along the line of "if it ain't broke, don't fix it!"  The A-65 is pretty low demand for voltage, but internal mag wear still occurs, primarily due to fouled spark plugs due to 100 octane lead fouling or the sooty burning of auto fuel.  I feel that there is a stronger argument to be made for 'when in doubt- DON'T!"  Most concerns over mag maintenance are financial- it costs money to inspect a part which appears to be working.  From the owner's standpoint, there is a value associated with the mechanic replacing a physically broken part versus working on a part which is demonstrating no problems. 

There really is no "pat" answer for your question.  I've seen thousands of failed parts over the years and nearly all of them failed due to neglect more than anything else.  My viewpoint is that the 500 hour inspection is a good thing, but you and your mechanic will have to work out the details on how to proceed.  In the end, the inspection is more common sense than any legal requirement. 

More information on Slick inspection schedules can be found in Service Bulletin SB1-86.  Here is a link to an article I wrote on magneto maintenance and troubleshooting which may be of use: 

Harry


A-65 Data Plates

I'm overhauling the A65-8 on the only remaining Taylorcraft in all Mexico, tail # XB ANC Serial # 7036, and I even bought a new data plate from Fresno.
I have engraved all the blank spaces in the data plate except for "P.C."  Please, do you know what P.C. means? or what I should engrave?

The PC means Production Certificate.  For the A-65, the PC is 7. 

Harry


Carb Leaking/Stumbling, Some Thoughts on Auto Fuel

[I can't find the original email that Harry's responding to, here, but it's pretty obvious where the questions ran - RJW]
If fuel is dripping out of the carb, the only source is past the valve.  The float may be riding too low, or, more likely, there is leakage between the valve and valve seat.  If the valve and seat are the metal type, then the mating surfaces can be lapped and most of the time this will stop the leaks. If the valve is rubber tipped, it is a more difficult repair, usually ending with the metal type valve being installed.  Be prepared that the carb may have to be opened a couple of times to get the leaking sorted.  In some cases, the leaking is something you live with.  The carb on my A65 drips about a teaspoon after each flight and I just put up with it. 

The stumble is another issue.  I'm guessing that the air bleed holes which provide the transition from idle to full throttle are plugged, or that internal circuit is obstructed.  Once again, the carb needs to opened to repair this condition. 

Auto fuel is another mixed bag of problems.  My A65 runs poorly on auto and much better on 100 octane.  The auto fuel burns very rich and leaves a lot of deposits on the cowling and plugs.  I have never been able to correct this problem on this engine, despite having yanked the carb on and off a half dozen times.  I fly 100 hours a year in this plane and I figured that the overall cost difference between a years use of auto vs. 100 is $300.  To me, solving my problems for $300 is worth it. 

Most of the parts sold by Woody Herman are in an "as removed" state.  Woody is a good guy, but will often say that the parts look good, or he will refund you if you are not satisfied.  Basically, if he sells me a part that is not recently overhauled or yellow tagged, I consider it a core and get it overhauled.  If you bought a carb that was not overhauled, it probably needs to be overhauled.  One of the problems with the Stromberg is that it is labor intensive due to the valve.  Most shops have to open the carb a couple of times to get the valve seated right. 

Harry


Overheating Cylinders

Sir, I have an ercoupe w/85 Continental. Noticed that #4 cyl. ( left front cockpit view) shows signs of overheating next to mounting flange area. A compression test indicated 78/80, we did a bore scope insp. and noticed carbon buildup on top end of piston, also plugs show a tan color. the bore did not show any defects. other cyl. appear ok.The engine runs smooth and has good power.
I do have an issue with oil consumption, no leaks can be found on the engine. I did install the breather elbow extension in the front eng. case. In fact that's why I had the cowling of when I noticed the temp. problem with no 4 cyl. The engine only has about 75 hrs since rebuild by a previous owner.

By signs of overheating do you mean bubbled paint or flaking paint? Usually, the only reasons that a cylinder will get hot is due to the use of incorrect rings, ignition timing, or possibly an induction leak. 

If you have a chrome barrel cylinder (identified by an orange paint band on the cylinder base) cast iron rings must be used.  Chrome rings are used with plain steel barrels.  If a chrome ring is used in a chrome barrel the friction will be very high and high heat and cylinder scoring will result. Oil consumption will become very high, also.  If steel rings are used in a steel barrel the rings will wear very fast, but usually not get very hot. 

It is possible that all of the rings on that piston were broken on installation and the burn mark on the cylinder is from hot gasses getting past the rings.  This condition should be found during a compression check. 

A clue to ring wear is low compression and oil that gets very dirty, nearly immediately after an oil change. 

High oil consumption can also be caused by worn valve guides, and is actually a very common oil consumption problem, especially in the Continentals.  In the worst case, if too much oil is being drawn through the guides, then the octane value of the fuel can be lowered and detonation can result.  The signature combustion features are blackish colored wet plugs and significant amounts of yellowish tan oil coke build up. 

If the mags are timed wrong, typically too retarded, the CHT can get very hot.  However, mag timing would be a problem on all cylinders, not just one. 

An induction leak on one cylinder would cause a lean running problem, but the cylinder head would tend to get hot more so than the barrel. 

Let me know if you need any more info. 

Harry


Power Loss at Wide-Open Throttle

I am  having a problem with my wide open performance of my O-200 engine . At  WOT it does not have as much RPM as it does when I back off about  1/4" .Timing is set at 30 BTC and am using a MA-3SPA carburetor .At WOT  I have tried leaning which did not help . The engine is an O-200 with a -8 accessory case.
I'm guessing that the engine was converted with the Don's Dream Machines STC.  I'm also guessing that it is on a homebuilt. 

The -8 case alone should not affect engine RPM.  However, carburetion, timing and prop will.  The stock timing is starts at 26 degrees.  Back the mag timing to 26 degrees and see if the rpm loss continues- if it does, it's probably not the timing.  However, I have seen many times when too aggressive timing will reduce performance.  30 degrees isn't all that excessive, but checking timing is a start. 

Related to the timing, was a stock cam used, or was the cam re-indexed? Re-indexing the cam is a relatively common technique, for air racing engines, but the engine will not make torque below 3000 rpm in some cases. 

On the carb, is it a one piece or two piece venturi?  The one piece venturi was notorious for rpm loss.  The fix was a new main discharge nozzle called the "pepperbox" nozzle.  Basically, it had more holes and atomized gas better.  Another way to check if the nozzle/venturi combination is at fault is to lean the engine at high rpm.  At base altitudes below 2500' msl, leaning the engine should have little or no effect.  If the engine picks up rpm at 800' msl by leaning, then it is a likelihood that a pepperbox nozzle is required. 

Finally, the prop pitch may have something to do with it.  The prop may be stalled at max rpm and unstalls at a bit lower rpm. 

Lots of other issues related to induction, airbox design, etc. 

Harry


O-200 GPU Cranks

Hi Harry, I have a chance to get an 0 200 GPU crank that is new. What is the difference between this crank and a standard 0 200? I am using it on a Midget Mustang with the C-85 case etc... Any help you can give me would be greatly appreciated.
The O200 GPU crank is a relatively poor choice of cranks.  A standard O200 crank has a centering hub which helps center the prop and actually provides some strength at the prop.  The GPU crank is flat and has no center hub. The GPU crank also is not set up for prop bolts.  The GPU does have short  studs which can be pressed out and regular prop bushings installed.  GPU cranks have not gone through the quality inspection and magnuflux inspection that aircraft parts go through. 

More than likely, you are going to put a prop extension on this crank, and I would not have strong confidence about the flange.  However, many hombuilders have used the GPU crank with no problems.  I would never use one, if that means anything. 

If the GPU crank looks like an O200 type with the center boss and aircraft prop bushings, then no problem. 

Harry


Fuel Injection

I am planning to do the C85 case and pistons with the 0200 crank,cylinders, rods etc... My local used parts guy says he has a 0200 fuel injection system that would be perfect for this application. Is there a system for the "0200" I am building that would work? The system he has did come on an 0200 or a C90 or something.
There was an system made by Ex-Cell-O which was a fuel injection for the C-85 and C-90 series.  The system weighs about four times as much as a carb and is more complicated.  Take a look at it before you buy- there are a lot of parts to the system.  You will need a special cam, throttle body, pump, lines, linkages. 

The icing on the cake is that parts are extremely hard to find.  I am restoring an Aeronca L-16 which used the Ex-Cell-O as a stock part and I have been scrounging parts for several years to get a good working unit.  As long as the system is in good repair, it works ok, but if it is not, then it is misery.  Most of the fuel injections units have been retired from service.  The only reason that I am pursuing it is due to originality.  I am also willing to accept the potential problems.  If you want absolute reliability, then the Ex-Cell-O is not the way to go. 

If you are not going inverted, a carb is dirt simple and works.  You can get parts all day long and every repair shop can fix a carb.  The Ex-Cell-O is a pretty crude unit and I don't think that it adds any power at all. 

Another option is the Ultra Carb from Sonex or an Ellison throttle body.  Both provide good inverted results but are a bit finicky to get dialed in, at least initially.  Once the units are jetted and metered right, they stay spot on indefinitely.  I tend to prefer the Ellison as it is light and has been around for quite some time.  The only negative is that the mixture control is not linear.  Most of the mixture control range falls within a narrow limit of the control travel. 

For whatever it is worth, I have a Cassutt with an O200 and I use a good old Precision MA-3 carb. 

Harry


Intermixing Cylinder Types

What do you think about putting a new Cont cylinder in with three chrome cylinders? I have one that is cracked and a re-built cost about $550.  The new cont. cylinder will cost about $635.

Personally, I see no problem with intermixing cylinder types.  There is a theoretical friction difference, but the A65/O200 is not running to NHRA dragster engine tolerances.  I have personally mixed cylinder types with no discernable performance difference. 

Harry


Adding a Generator

I am sure you have been asked this question thousands of times but I can't see an answer anywhere. I am building a Midget Mustang and have a C85-8. Is there any way to put an alternator/generator on this engine? I have a machine shop so machining and TIG welding are no problem. I want to be able to fly this plane cross country to attend fly inn's and visit people and don't won't to be limited. Could you please give me some guidance?
The quick, no whiskey, bite the bullet answer- no.  You could convert the -8 to a -12, but it is quite a lot of work.  A new accessory case and accessory drive gears are going to be needed.  The -8 and -12/O200 accessory case have different mounting hole layouts, so you would need to do some indexing to get everything to align properly.  The magnetos are a different rotation between the -8 and -12/O200 and would need to be replaced (mag rotation can't be switched).  The ignition harness would also need to be changed or altered to match the rotation of the mags.  There are some other details, but the conversion is conceivable. 

With today's prices, the cost of the parts alone would easily be in the $3500 range, depending upon your scrounging ability. 

The good news is that the -8 engine is a fairly desirable engine and is easy to sell if you need to generate cash for a -12 or O200.  You should be able to sell your engine and move to an O200 or C85-12 with no problem. 

Harry

[RJW.... the questioner came back with a follow-up:]

I don't have the mags or harness yet and I have both accessory cases. I would need to buy the -12 cam and crank gears. I guess I was just wanting to know if the -12 accessory case could be mounted to the -8 case? Are there spacing problems? Have you seen this done? I still need a crank, mag's and the intake system so now would be the time to make the change if I can do it.

If you had a -12 case, the only extra parts would be the big gear for the cam (530535), crank gear (35016) and the two magneto drive gears (p/n 36066) and mags (Slick 4301). 

Otherwise, the bolt holes to mount the -8 case and the -12 case are in different locations.  There is a conversion to mount the -8 accessory case on the -12, so I would reason that the reverse could be accomplished, as well.  Another subtle problem would be that the stock rear accessory case gasket would not match up.  I don't think that there are spacing problems  It is critical to get the mag holes in the case centered on the crank gear. Any offset will result in a side load on one of the mags. 

Another problem that jumps into my mind is that the -12 and O200 cases have a pair of bosses which extend upwards between the motor mounts.   These bosses support the top of the accessory case where the starter mounts.  You would have to weld something like this on the case. 

Harry


A65 Horsepower Increase

What is the best way for me to get about 80 to 90 hp out of my A65 engine?  I have an A65-8 with 42 smoh  that I need to tear down and inspect since it has sat for 2 years without  being run since I have it tore down.  Maybe I could bump the compression or whatever.  Please let me know the best most reliable way to do the HP upgrade.
The easiest hp increase with the minimum amount of work is the conversion from the A-65 to A-75.  The change is pistons, connecting rod work and carb re-jetting.  To get more than 75 hp will require welding to the A-65 case, extra studs, and special experimental pistons.  The A-65 would need a flange crank as the taper crank is not capable of supporting much more than 75 hp.  Along with the above, you really need to magnaflux the crank and zyglo the case and balance the reciprocating components. 

Upping the output of the A-65 is not a casual affair.  If you compare the A-65 to the C85/O200 you will see how lightly the A-65 is constructed in comparison.  Some homebuilders have dropped in experimental 9.5:1 pistons, turned up the rpm to 2700 to 3000 and accept the unknown risks.  Consult lycon.com for info on the pistons. 

Harry


Oil Mist

Harry, I have a Continental 0-200 engine with @ 3600 hours. It has chrome cylinders which have been worked on to some extent in the past. I'm taking her in for the annual in about two weeks. The AP I have been working with since I bought her in July of last year said at the last oil change that although the compression was good the cylinders should be replaced with after market new cylinders that are available for about $700 each. The problem is the oil mist that covers the engine compartment between oil changes ( every 25 hours ). He said the pressure in the crankcase was too high causing the mist to be forced out wherever it can find a spot. I trust this man so I don't think he would steer me in this direction without merit based on his experience, about 30 years.
After investigating on the Internet and seeing a few advertisements in AOPA Pilot magazine it looks like I may have a blow by problem which an air/oil separator might help or some modification of the crankcase ventilating system might be in order. This is my first airplane but I know from other engines that if the oil level is too high the crankshaft will turn the oil into frappe and if the PCV valve gets clogged and dies you have problems.

Can you shed some light on the subject? I appreciate any help can give me.

Is your engine at 3600 hrs since overhaul?  If so, there comes a point where you can only push parts so far.  What is your oil consumption like?  You may have good compression, but the valve guides could be show, which would result in high oil consumption. 

The crankcase can be pressurized by low compression cylinders.  In effect, the air being compressed in the combustion chamber leaks back into the case, causing high case pressures.  An air/oil separator can be a good vent tube oil collector, but one has to wonder what the source of the oil is as opposed to installing a device which masks the root cause of the problem. 

The Continental vent tube is known to be a bad design.  The outlet sits flush with the case and the splash and vapor oil can migrate into the tube and overboard.  Typically, this results in oil on the belly, not in the engine compartment.  Continental or Cessna makes an aerobatic vent which was used on the Cessna Aerobat 150.  This vent has a longer tube which extends into the engine and is less likely to provide a path for the oil to migrate from the engine.  The Piper Cub Club and Aeronca clubs have members who solder copper tubes onto the stock vent tube to achieve the same result. These repairs are not FAA approved, but hundreds and hundreds are in service.  I find that the modified vent tube solves most oil blowby issues. 

However, the above fix addressed oil out the vent onto the belly of the plane.  Oil in the engine compartment could be due to deteriorated engine seals and gaskets or, in the worse case, a crack in the crankcase.  The most common seal and gasket issues are mag gaskets, tach seals and generator/ alternator gaskets.  The best way to find leaky gaskets or cracks is to wash the engine down with solvent, run the engine for  bit, and then shine a black light on the engine case and around seals.  An oil leak will turn up as a black line which is visible under black light, but not always under natural light. 

I'm betting that a seal or gasket is blown which is causing the fine mist. An air/oil separator will not solve that problem. 

Harry

[RJW.... the questioner came back with a follow-up:]

Hello Harry , thanks for your quick reply. The 3600 hours is total time, 1300 since last major. There is some greasy residue on the underside of the fuselage but not fresh oil if there is a difference that can be determined. The oil consumption is about one quart every 10 hours that's not a charted Figure just an educated feel. Two to two and a half quarts between oil changes. I guess my immediate consideration is the cost and necessity of replacing the cylinders. If the problem is gaskets leaking and the cause is excess pressure in the crankcase wouldn't the heads need attention instead of the cylinders if the compression numbers look good?  He said he looked at the engine but could not determine a spot where it was apparent that oil was leaking.

Your oil consumption sounds ok.  I would still opt for the breather mod as opposed to an air/oil separator.  You might want to check the Cessna 120/140 site-www.cessna120-140.org.  Oil blow by is a common thread of discussion. 

Calendar time is the enemy of gaskets.  They simply break down over time.  I have an engine with 200 hours which was overhauled 30 years ago.  It runs great, but is covered with oil.  I'm pulling it off this month and tearing it down simply to clean it up and install a major overhaul gasket set. 

Finding oil leaks on aircraft engines is a pain.  There are too many places to leak and most engines run 20 years or more between overhauls so the gaskets go rotten.  Bottom line- there is no pat answer for your question, you just have to kind of pick around until you hit the right answer. 

Harry


A65 Intake Spider Restriction

I was looking at a couple of Continentals intake spiders and am wondering why the one for a C65 has a restriction a little way above the carburetor flange where one for a C 85 is full size all the way up?   Is this a way they protected the 65 from being pushed too hard? What would the result be if the restriction was removed?
Since the A-65 came first in development, I'm guessing that the Continental engineers sized the A-65 spider appropriate to the engine design.  When the C-85 cam along, engineering probably upsized the spider. 

The A-65/C-75 can pick up 25 to 75 rpm with the C85/O200 spider.  I've never noticed any significant performance increase other than a few more takeoff rpm.  The rest of the power range seemed to be the same.  The problem is that it is not legal to install the larger bore intake on the A65 [for a non-homebuilt...RJW]. Modifying the 65 intake is still kind of shaky for a legal engine, but porting and polishing companies like LyCon in VisaliaCA seem to have an approval for such work.  Maybe they could do the work and keep your part legal.  Otherwise, no problem if you have a homebuilt. 

Harry


Cylinder Temperature Variations

Finally my A85-8 hybrid engine is flying...this time WITH oil pressure. I got 4 1/2 hours flight on it and the oil pressure  is great (even at 210' oil temp I saw Sunday while climbing to 7000').  There is something that bothers me though...the cylinder head  temperatures are not equal. Normal cruise #1-350' / #2-400' / #3-300 /  #4-350...For climb add 50 degrees to all cylinders... here is the  problem on a long shallow descent the #3 goes to below 200'. Is this not too cold. Also it would be nice to get the #2 to be 50" less. My question is. Should I leave well enough alone or try to equalize them. I could block-off part of the #2 cylinder and barrel where the air comes in the cowling inlet to warm #3. Also my other idea was to put a 1 1/4" tube (1 1/4" is what I happen to have on hand) between my left  and right box baffles. This should equalize the inlet pressures..No???  Another possible problem...WOT yields 2550-2600 RPM...right on the  money for a C85...but between 1800 and 2000 RPM there is vibration. Is  this normal? Could this be the prop vibration? Prop is a Sterba  62"diaX60"pitch.
The temperature spread is not all that bad.  I have seen as much as 200F temp spread between cylinders.  Also, most probes can be out of calibration by 50-100F.  The spark plug gasket probes typically read about 35-50F low, also. 

Generally speaking, the number that you are seeing are in the ballpark and not out of range.  Let the engine run for 25 hours and keep a record- if you honed the bores or installed new rings it will take about 25-50 hours for everything to seat and for the friction to equalize. 

I've got some good links to info on CHT issues which I will dig up and post to the group. 

Regarding the vibration, this could be a wide range of issues from the wing wires shaking at a specific airspeed/rpm, cowling buffeting, to the prop shaking a bit.  The easiest way to start to make a change to the vibration is to turn the prop blades 180 degrees.  On starter equipped engines I try to clock the prop around the various positions to find a smooth point.  This won't work on a hand prop engine as the blade always has to be clocked to TDC or so for a good swing position. 

Kind of like that old joke, "Doc, my arm hurts when I hold it like this!" "Then don 't hold it like that!"  You may have to avoid that rpm range if it shakes too bad.  The Van's RV series (as well as many factory built aircraft, like the Grumman series) have rpm restrictions in particular power bands due to torsionals and harmonics between the engine/prop/airframe. 

Harry


C-85 Fuel Injection

Is anyone else flying a fuel injected 85? I need the manual that covers the fuel injection system. Know where I might find one of those? Thanks.
I have run the fuel injection on the 85 and it is not quite what you would think, at least in modern terms.  Modern fuel injection does improve automotive engine operation, and some aircraft engines with relatively modern fuel injection have improved performance.  But, the old Ex-Cell-O is far from modern.  If you had all of the components for the 85 injection and a cab set on a table next to each other, the immediate observation is the obvious complexity and weight of the injection.  The injection mounts a pump on the front of the case, there is a flow divider and throttle body, and injector lines.  The carb is a much simpler and much lighter installation and has clearly had much more success. 

From the service standpoint, there are few, if any parts, for the injection readily available.  Everything must be scrounged, and all of it is used. Most of the remaining used parts were worn out parts which were never thrown away.  If you can find parts, you will need to find a shop willing to work on the injection.  There are manuals available, but the Ex-Cell-O is nearly extinct, so it will be a learning experience for most shops.  However, I'm sure that the Aeronca list can provide some shops familiar with the system. You are more likely to find a way to get your carb fixed 100 miles from home than your Ex-Cell-O fuel injection. 

Operationally, there is a reason that the injection never caught on.  Unless it was in proper tune, it made the engine very finicky to start.  I found that my engine would not start unless impulse coupled magnetos were installed.  I don't think that it adds anything to engine horsepower and increases the weight and mechanical complexity of the engine. 

I approach my injected 85 simply as a mechanical curiosity.  I'm a pretty experienced A&P and most of my aviation career has been spent working around engines, so I don't look at the Ex-Cell-O as a benefit.  It is an antique gizmo which adds zero performance, makes a simple carb based engine more complicated and less unreliable due to the extra complexity and lack of good spare parts.  It is mechanically interesting and different, and that is about it. 

Harry


GPU Engine

I have found a new GPU engine it is a 470 CI rated @ 175 HP I forget the designation (Continetal 200 or150}?
The GPU you are looking at is probably the one based upon the military O-470 used in the L-19 Bird Dog and the Beech Mentor.  The military O-470 series was further based upon the civilian E-185/225 series.  These were very good engines, but kind of pricey to overhaul due to lack of volume on the spares, especially the main bearings.  I am not too familiar with the six cylinder GPU engines, so maybe the parts supply is not too bad, but I'm not sure.  I don't know much about what is needed to convert the GPU to aircraft use, but I believe it is simpler than the O-200 GPU.  The O-200 GPU has a different engine case, crank and cylinders which makes it difficult conversion.  I think that the O-470 GPU is more aircraft-like and needs less work to convert.  Many of the O-200 GPU engines I have run across are like new and virtually no hours as they were used for backup power.  The O-470 GPU will probably have more hours as they were used for start carts for jets. 

Thislink may have good info on the GPU engine.  This company specializes in the O-470 GPU. 

On the other hand, the parts supply for the standard aircraft version of the O-470, especially the O-470-R, is fantastic.  The prices for core O-470 aircraft engines is not too bad, maybe $4-$6K.  The O-470 tends to be sold for way less money than a Lycoming engine core.  I like the Lycoming 540 series, but the 470 is a darn good engine, also.   The key is that you may have more into overhauling the GPU, despite the low acquisition price. Another advantage to the aircraft version is that it lowers the amount of hours that the FAA will require for test flying because it is a certified component. 

Keep in mind that the Aussie fellow is fighting a different set of economics.  Everything costs twice as much in Oz due to shipping, import duties, etc, so it may have been cost effective for him to convert the GPU than use a standard aircraft engine.  Also, I do know that a fair amount of GPU engines were fished out of Viet Nam by an Aussie, so spares may actually be a bit easier to acquire there.  My day job is with an Australian aviation company, so I'm pretty familiar with the market there. 

My gut feeling is that the standard aircraft O-470 will be a better deal in the long rung, but kind of hard to tell without seeing the core you want to use.

Harry


Miss With Application of Carb Heat

I have a 1946 ercoupe with an 85 continental in it, the problem I am having is when I apply carb heat I get a miss in the engine and it runs rough, when I push it in the engine smoothens out. I thought that there may have been a hole in the muffler causing raw fumes to go into the carb but there was nothing wrong with the  muffler. I put in new plugs and checked the mags and they are alright. It has marvel carb
When carb heat is applied, the mixture becomes more rich.  With the rich mixture, the spark plugs can foul and misfire.  If the magneto internal timing is off, then the mag can't generate a hot enough spark to jump the fouled gap.  If the spark plug gap is too wide, then the plug may misfire. If you have a combination of weak mag output and wide spark plug gap, then the rich mixture will certainly cause the engine to miss.  The Marvel carb, especially one that has not been overhauled in a while, tends to leak past the accelerator pump, and when the carb heat is applied the engine will become overly rich. 

On the back of the carb there is a thumbscrew to adjust idle mixture.  If the idle mixture is adjusted too lean, the engine will backfire and run roughly when the throttle is at idle or low power setting.  Sometimes the idle mixture is leaned out too much to try to correct a rich running problem due to a leaking accelerator pump or leaking primer. 

Precision Airmotive is the current manufacturer of the Marvel carb and companies like Aero Recip, Leavens, or Progressive Aero can do repairs or sell parts. 

Harry


Throttlebody Fuel Injection

I am the president for the EAA 668 Chapter in Iceland.  One of our member has a Buddy Baby lakes with an O-200.  He is using an Ellison thottlebody which is mounted traversly pulling the slide to the right.
The left cylinders are always running rich. The airbox is similar to a piper Pa18 using carb on a C-90 or O-200. Can you recommend an airbox and filter for this application?

Can he increase the hp by installing C-85 pistons?

The first airplane I built was a SuperBabyLakes.  I built it as a High School project as a teenager. 

The Ellison is very sensitive to airflow.  I had one installed mounted forward on a VW engine in my Sonerai and had similar problems.  The only way I fixed the problem was to put a 6” extension between the throttle body and the induction spider.  At the spider, I welded an X shape to straighten out the airflow.  The Ellison also requires at least a 4” straight run on the intake side.  The point is, the Ellison is very sensitive to incoming air turbulence and outflowing turbulence.  Another possibility is an air plenum before or after the throttle body. 

I also used a NASA scoop on for the intake and found that it is a very poor choice unless mounted directly on the bottom of the cowling, facing directly into the incoming airflow.  The NASA scoop loses most of it’s intake effectiveness it becomes oriented 10-15 degrees off of the dead center of airflow.  In my installation, I had the scoop mounted on the left side of the fuselage the engine would quit in left turns as the NASA scoop was turned from a forward intake position.  It would run very rich in right turns.  When oriented to the bottom, forward facing portion of the cowling and mad twice the size as recommended, it worked very well. 

Ellison is well informed of the airflow issues with their throttle body. There used to be a guy named Chuck in the product support area and he was always helpful in describing the operation issues of the throttle body.  He wasn’t helpful in the airbox design other than he said that the air needed to be straight and non-turbulent.  To be honest, once I followed his basic advice, the throttle body worked well. 

I have had excellent success bolting the Ellison to the stock O-200 intake spider.  Is there any reason your friend can’t do that?  I would highly recommend that application. 

The C-85 pistons will add a bit more horsepower, maybe 5-8 hp.  No dyno tests have been done, so the improvement is speculative.  The perimeter of the top edge of the piston must be machined to a 45 degree bevel, ¼ -3/8” wide for clearance purposes. 

Harry


Gear-Driven Fuel Pumps

Do you know of a gear driven fuel pump that could use the vacuum pump gear on a continental 0200.

The old Ex-Cell-O injection used a fuel pump at the vacuum pump, but it is heavy and no parts are available.  The most typical fuel pump is the old lever style which mounts on the forward side of the engine or an electric boost pump.  Other than that, I am unaware of any other gear driven pump.

Harry


Special Oil Strainer Socket

Hello! I'm enjoying your 'Hints and Tips for Small Continental Engines', which I've only just discovered.  I've owned an A-65-8 on a 1943 Piper L-4 since 1996. I've always wondered about many things pertaining to the engine. Reading through your tips, it seems that mine is a healthy little beast.
My questions: Does anyone make a socket specifically to deal with the oil strainer? Has anyone ever made a replaceable cartridge type oil filter that replaces the original strainer?

I am not aware of a special socket.  I use an open ended wrench, cut off in the middle to make it shorter.  The strainer should be tightened just enough to partially compress the copper o-ring.  Sorry, the wrench is in my toolbox, so I don’t recall exactly the size (1 ¼´ sticks in my head, but I’m guessing). 

El Reno Aviation sells a spin on oil filter adapter and it works quite well, provided you have the room to fit it up.  I think that Wag Aero and Aircraft Spruce carry this adapter in their catalogs, also. 

Harry


Stumbling A-80 & Adding an accelerator pump

Our chapter was donated a Skyhopper by a former member. It has an A-80 and has a troubled powerplant coughing history which may be caused by the lack of an accelerator pump carb. Any comments on modifying Stromberg carbs for accelerator pumps?
I don't think that you can modify a carb for an accelerator pump- the housing for the accelerator mechanism is cast into the body of the carb. You may be able to mix and match parts, but I suspect that is easiest just to use a complete, correct carb assembly. 

Your stumble is probably due to blocked or obstructed bleed hole.  If one of the bleed holes which serves as the transition from idle to higher power settings is blocked, the engine will stumble.  Another possibility is that the holes where the throttle shaft passes through the carb body are worn. If too much air is pulled through the holes, then the mixture will lean out and the carb will stumble until more fuel is available.  If the engine was previously used on a homebuilt, then perhaps the carb air box was too small. 

Harry


Case Magnetos

I fly a 1946 Aeronca 11AC with an A-65 Continental with Case magnetos.  I'm noticing what sounds like a periodic popping noise in the exhaust - most noticable on climb out when warm.  I've taken the mags off to clean, inspect and reset; but I don't know how to set the internal timing.  Do you just clean the contacts and set them to some dimension when fully opened? or some other setting (eg 'E' gap)  Also, how do you know if the geared components are installed in the proper position/alignment with each other?
The Case mags were not very reliable when new.  The single biggest problem is that carbon dust builds up in the distributor block area and the mag misfires to the carbon dust.  The carbon finger is attached to a spring in the center of the coil and wobbles quite a bit, making the dust. 

There are zero new parts for Case mags, and most of the used parts are worn out, so you have to work with what you have.  The point gap can be set to .010 to .012 to get you in the ballpark of running right.  Most likely, there is carbon dust in the mag- this was the single biggest problem with the Case mags. 

Another thing to check is spark plug gap.  If the gaps go beyond .016-.018, then the mag doesn't have enough juice to jump the gap. 

Harry 


A65 to A75 For Better Climb

I am not a small J3 driver. I weigh in at 275#. I have an A65 in my cub and am wanting to increase my climb rate. I have just installed wing tanks for range, and I know right now I need a new prop and I have to make a decision.
I have an opportunity to buy from an IA a converted A65 to A75 engine. The only problem I am struggling with is that this conversion took place approximately 30 years ago. This engine is in a crate, been stored inside and I have looked at it. There is no visible rust anywhere that I can see. There are no accessories with it nor any older log books. My IA friend is considering parting with it and I am thinking on getting it. Is there something I should do with my 65 to get that better climb rate? By the way my 65 is turning only 2150 at full power on take off and both mags are timed to 30 degrees BTC. A new prop is in order but I need to hear another thought on moving toward the A75 or doing something with my A65.

You will notice some difference between the 65 and 75, but it is not a huge difference.  To get a significant improvement in climb for a guy your size and a heavier airplane, you need to move to an 85 or O-200 100 hp engine. The 75, though, is better than nothing, and will work better than a 65 as long as the prop is pitched for climb.  Be prepared for a 65-70 mph cruise, though. 

You need to make sure that your tach is reading correct.  Wag Aero sells a digital optical tach for $50 or so which works great.  If your engine is only turning 2150, then you may have a cruise prop pitch. 

Used engines which have been lying around with no logs are a bit of a gamble, but not necessarily a waste of time.  That engine probably was going for $800-$1000 30 years ago, so I wouldn't pay four grand for it.  With no accessories or logs, I would start at $1200 and go to maybe to $2200, $2500. It all depends on how bad you want it.  It is somewhat of a seller's market for such things.  An overhauled engine means more than just rings and bearings.  Overhauled will mean that the rod bolts and nuts were replaced, new valve guides, re-ground tappets, re-ground rocker arms, new bushings in rockers, case, cylinders and accessory case dye checked for cracks, crank ground, valves ground, cylinder bores checked for out of round and taper, on and on.  Too many times, small Continentals are passed off as overhauled when just bearings, rings and gaskets were installed and it was painted to look nice.  Accessories will cost a bunch, too.  A carb, with no core, will run $1200 or more.  Mags will run $2200-$2500 with no cores. 

My word of caution is, this is not a top dollar engine.  But, the world is not awash with small Continentals, so it boils down to how bad you want it or need it. 

Converting to higher horsepower is not a piece of cake, either.  A C-85 through O-200 will require a different prop and maybe a different motor mount.  The quickest way to give you some extra hp is to go with a 75. Forget about the A-80 conversion as the pistons are very heavy, making the hp conversion not as efficient at the A-75. 

Harry 


O-320 Rough Spot

My Lycoming O-320 powered Piper PA-20 has a "rough spot" between 1200 - 1400 rpm.  The engine will not accellerate through this area unless I apply carburetor heat. I can reduce power into this area.  If the engine is running between 1200-1400 and I apply carb heat, I get an increase in rpm.
I've thought that I was sucking air (induction leak) so I leak checked the primers and intake manifold.  I found a couple of leaks and I fixed them. But the problem still exists.

I installed a Major Over  Kit in my MA4-SPA carb with new venturi.   The problem still exists.

I'm thinking maybe the idle mixture know is allowing air to enter the carb.

It could bee that you are pulling air in through the hole in the carb body where the throttle shaft passes through.  If the clearance becomes too great, then air is sucked by the shaft and the mixture becomes lean.  This may be the case as carb heat would tend to enrichen the mixture (the oxygen molecules become less dense to the relative fuel).  Another possibility is that the bleed holes which transition from idle to full power are obstructed. 

Buried within the Lycoming Service Bulletins are a couple of SB's regarding rough running on early O-320 engines.  There was a mod to the sump intake tube and different jetting for the carb.  Both of these issues addressed rough running engines.  The straight O-320 and the O-320-A2B were affected, both of which would be applicable to your airframe. 

You might want to contact Mahlon Russell from Mattituck.  His e-mail is mahlon_russell@teledyne.com.  Mahlon is much more of an expert on Lycoming engines than I am.  Mahlon moderates a Lycoming discussion group at Yahoo, providing the same type of info on the Lycs that I do with the Continental. Mahlon is very good at answering e-mails- he's a good friend, so feel free to mention that I sent you. 

Harry 


Engine failure post-mortem

Hello Harry: I think I already know the answer to my question but I would like your opinion. My A65 quit on me last night at an very inopportune time. Until now this has been a rock solid engine.
I was on downwind leg doing touch and go's doing about 2000 rpm. The engine lost about 1000 rpm for about ten seconds then stoped dead, didnt wind down, just a dead stop.

The good news is that I made the feild and the plane and me survived. I suspected a engine seizure, but when I got out of the plane( after kissing the ground ) the engine seemed to turn over ok, maybe a little tight? It was late in the eve, so I did not have time to do any checks of oil level etc, the oil temp at the time was 200 F.  I do not know what the pressure was.

I think one of the pistons may have seized up, what do you think?  If one did seize, what would you recomend as a repair procedure? Does the whole engine have to be torn down? I am assuming that the engine did not run out of oil I took off with 3.75 quarts the day before and had only flown 2 hours since then. I know a lot of unknowns here, please help

I always feel like a doctor at this point- I can give I to you easy or give you a bullet to bite and give the bad news quickly.  Find a bullet to bite- 

It could be that the engine quit due to carb ice.  If you have a wood prop, it is possible to have the engine wind down and stop fairly quickly. Impulse coupling springs can break, also, but the engine usually runs rough before quitting.  It could be that something went through the carb or the float stuck and the carb ran out of fuel.  This happens from time to time. 

If it is a bearing problem, you don't want to run the engine and risk further damage.  The first step is to pull the oil screen and look for debris, especially metal.  If the screen is clean, that may not clearly indicate no problem.  A common issue is a spun rod bearing, and your engine may not have run long enough to dump metal into the system.  Pistons don't usually seize, but if there is a piston problem, there will almost certainly be a lot of aluminum debris in the oil screen. 

Bottom line- if you suspect any damage to the bearings, don't keep running the engine as you will cause more damage.  The only real way to determine what is going on inside your engine is to tear it down.  The good news is that a gasket kit is less than a couple hundred bucks.  If no mechanical problem is found, then the parts cost is low, just re-use the existing bearings.  Technically speaking, you do need to have an A&P do the work or observe and agree to sign off on the teardown and re-assembly. 

I would strongly recommend that you get an experienced A&P involved.  I'm making some recommendations over the internet and haven't seen your engine, so I'm really just guessing as to the nature and extent of your problem. Unfortunately, there is no pat answer for a potentially serious problem such as you have described, other than have an experienced mechanic take a look at your engine. 

Harry

Follow-up #1

Here is what I found out last night.
The engine did not run out of oil. The engine turns over freely. The only obvious problem was a loose clamp on a intake hose, by loose I mean backed off all the way. Could be an air leak here causing one cylinder to run lean and hot?  Pulled all the plugs and they all look good no sign of lean running, all nice and tan colored.

I bit the bullet and started her up, runs nice, oil pressure on start up is about 30 psi, always has been for the two years I have owned this plane, I was told that this is normal? I ran the engine for about twenty minutes on the ground, cylinder temps were around 300 to 350. Oil temp got up to around 200 degrees near the end of the run. Oil pressure steadily dropped as temp went up. Normally at cruise rpm my oil pressure was around 15 to 20 psi depending on outside temp( I am running 80W by the way).

Today during the test , @ 2000 rpm oil pressure was only 10 pounds @ 200 degrees. It seems to me that this is way too low and the engine got tight and stopped.( referring to the flight on Sunday night, not the test run, the engine ran the whole time during testing).

I don't know if any bearing damage occurred, I will pull the screen and look for metal. Is any amount of metal normal? The good thing is that this is not a certified aircraft and all maintenance can be performed by myself. I have rebuilt auto engines and do have the teardown manual. Where would I get a gasket set and bearings, etc. Do you know of any place in Canada? Thanks again Harry, your knowledge in invaluable.

10 psi is on the low side.  If the intake clamp was loose, the rubber seal was probably still sealing.  Once those rubber tubes have been clamped in place, it takes quite a bit of force to move them out of position.  However, if the tube was completely dislodged, then the engine would probably be way too lean and quit. 

You really should not see much metal in the screen.  The screen is a pretty big rock catcher, so by the time that it catches any debris, you have a serious problem. 

You are approaching the "when in doubt- don't!" phase of thinking. An unexplained engine power loss is a pretty big concern.  A sudden change in oil pressure, whether it is linked to the power loss or not, is a point of concern.  You have the classic makings of a progressive failure of some sort.  The initial warnings are not clear, and conditions worsen with each run of the engine with no clear indication of the root problem. 

If there is any question at all about oil starvation or bearing displacement, then the only solution is to open the engine and probe around. Honestly, you may find something, you may find nothing.  A benefit to opening the engine is that you will have a concrete answer by physically inspecting the parts, despite the chance you may find no problems.  Finding no problem is actually a concrete answer and forces the investigation towards other directions.  On the other hand, you will have no concrete evidence of the internal condition without an internal inspection. 

The engine teardown is pretty easy and can be accomplished easily within a weekend.  The only special tools you need will be a set of cylinder base nut wrenches ($50-$75) which can be found from Aircraft Tool and Supply and other suppliers.  A gasket set can be bought from Progressive Aero in Kamloops, 250-376-6226.  Ask for Brad Ford in parts- he's a friend of mine. Fresno Airparts sells A-65 parts and gaskets and their ad runs in the first page or two of Trade-A-Plane.  I don't have their number handy, but I'm sure it can be found at www.trade-a-plane.com <http://www.trade-a-plane.com/> . Progressive can fix you up for sure, though. 

I have another acquaintance in VictoriaCanada who has rebuilt a Continental and is very familiar with the engine.  Drew Fidoe can be contacted at dogsbody@telus.net.  He will be more than willing to share info, also. Otherwise, if you give me your location in Canada, I can probably dig up other contacts. 

A final note:  you mention that this is on an experimental plane.  Do you have any details on the airframe, hours in service, propeller type, etc?  It could be that the engine stoppage was a fuel venting issue and the oil pressure issue is an unrelated problem. 

Harry 

Follow-Up #2

I got my 65 apart today, pulling off the jugs, I found that #4 cylinder the piston had seized. There is a small transfer of material onto the cylinder wall. I am hoping that the machine shop can hone if off.
Looks like lack of oil splashing on the cylinder skirt. I split the case and looked at the bearings and they are very worn, so that I presume is the source of my low oil pressure, leading to lack of oil splashing on the skirt. I have found a machine shop in Abbotsford that would be willing to machine my crank if it needs it.

I was also talking to a guy who says that you don't need to nitrate the crank in a 65.  From what I measured it is still serviceable, and all I should need is bearings and a polish. I don't trust my measurements, so I will let the machine shop take care of that. I am hoping they will hone the cylinders as well. I will need a piston for sure. It kind of sucks because the top end was done on this motor only 100 hours ago. Any advice you would have at this point would be greatly appreciated

It is pretty unusual to have an A-65 piston score the cylinder.  The overall oil pressure of the engine doesn't really affect the cylinder walls as the cylinders are lubricated by splash oil, not pressurized oil. 

You mention that the top end had been worked on. I wonder if the oil control rings were installed upside down?  The oil control scraper is supposed to scrape oil back into the crankcase, and then drag it upward on the compression and ignition stroke.  If it were installed in reverse the oil would be scraped off of the cylinder wall into into the combustion chamber, the oil would burn, and the plug would foul.  If the oil control ring is upside down, basically there is not enough oil on the cylinder wall and the piston will score the walls. 

The A-65 crank does not need to be nitrided.  But, the radius angle where the journal transitions to the crank is different that automotive applications.  If it is ground to automotive tolerances, the bearings will bind at the radius. 

Harry 

Update #3

Hi Harry: Thanks for getting back to me. Yes the top end has been worked on, about 100 hours ago. New rings, lapped valves, one new piston, not the one that seized, and some lifter bodies, again not on the cylinder that seized.
I know that the pistons rely on splash oil, but I thought that the lower oil pressure maybe would of reduced the amount of oil available to splash. The bearings were quite worn, so I think the clearances were excessive. I have the cylinders at Valley aero at Langley airport. They are going to check them out as well as the crank, hopefully all it will need is a polish. The amount of aluminum that transfered was minimal, and I think they can hone it out? The rings did not seize just the skirt, I cant remember if it was the intake or exauhst side( I am at work right now) and there were contact marks on the opposite side, as well but no transfer of material there. So I will need one piston at the least, some bearings if the crank measures out ok.

I talked to the automotive shop if they have to grind it, they will index the journals to match what I have now. I will replace the rings and rod bearings as well. I was suprised to see the cam did not use bearings!!

Is there any thing else I am I should be taking care of while I am in there? Are oversize pistons marked? I cant seem to find any markings on them. Also I did not mark the front of the piston while taking them out, are they marked for this as well?

There are no top and bottom to A-65 through O-200 pistons.  Some engines, like VW/Porsche types have a top and front orientation. 

Oversize pistons are available and are marked with M010, M020, M030 or whatever number to correspond with how many thousandths the piston is oversize. 

As I ponder this further, I am thinking that if the rod bearings and piston pin bushing in the rod were worn, then the piston "rocked" excessively and scuffed against the cylinder wall. 

Usually, the aluminum can be polished off of the metal parts. 

Overall, it sounds like you are on the right track and should be going again with moderate hassle. 

Harry 


Compression Limits

I have an A-65 on a Wolf Boredom Fighter. Total time is about 1550, with a complete o-haul at 1280. Current compression is 64,74,70,64 and checked when hot. There's no vibration that I can tell through the airframe but I was wondering at what point do I need to stake the valves or pull a jug?
Continental has a very detailed Service Bulletin on differential cylinder testing.

Within this Bulletin, there is reference to a calibrated orifice.  When the calibrated orifice is used to set a baseline for differential leakage, the low number may be as low as 50 psi. Informally, 60/80 is the general baseline as the point to start to look into cylinder condition. There are, however, guidelines for leakage past the rings and valves.  Generally speaking, leakage past the rings will yield a hissing sound in the crankcase which can be heard by listening at the breather tube or at the oil fill cap. Leakage past the exhaust valve will yield air hissing in the exhaust and the intake will hiss air through the carb. 

TCM recommends the Eastern Aero differential tester, but both US Industrial Tool and Supply and Aircraft Tool Supply sell differential testers with the calibrated orifice or just the orifice by itself.  Once again, read through the SB and you will get the general idea of how to interpret the compression. 

FAA Advisory Circular AC43.13-1A also provides some guidance.  Look for AC 43.13-1B, chapter 8. 

Finally, Aircraft Maintenance Technician just printed an article on this topic. 

The bottom line is that compression can be low, as long as the dynamic leakage past the rings and valves is not excessive.  More important than any hard number, if the parts which are required to seal the particular combustion cycle are bad, then the cylinder needs to be serviced. 

Harry 

Follow-Up

Where were those 50/80 limits derived from?
TCM has a Service Bulletin regarding compression testing limits.  The link for this bulletin is http://www.tcmlink.com/pdf2/SB03-3.pdf.  The FAA's AC 43.13-1B, Chapter 8 describes general compression testing. 

There is no "set" lower limit for compression.  The baseline to start to evaluate compression and overall cylinder condition is always 80 psi, though.  TCM SB03-3 details a procedure to calibrate the pressure gauge using a Master Orifice tool which will provide a baseline for a low limit relative to the atmospheric conditions particular to the moment when the engine compression is checked.  The low limit established by the Master Orifice tool can be as low as 50 psi, but there is no set limit.  If the low limit is established as 50 psi and there is no leakage past the rings, valves and guides as stipulated in the SB, then no problem.  If there is leakage past the rings, valves, or guides in excess of the limits set by TCM, then there is a problem. 

FAA AC43.13-1B provides a guideline that a differential pressure loss of 25% or greater (80/60 psi) is cause to suspect a problem with the cylinder. However, AC43.13-1B does not provide as much detail as the TCM SB in terms of dynamic leakage past the rings, valves and guides.  The 25% limit is simply a static check to yield a ballpark reading on cylinder compression whereas the procedures in TCM SB03-3 are more dynamic and, ultimately, yields a more accurate assessment of cylinder condition. 

Harry 


A65 Overhaul Data

I was wondering if you have the specs needed for rebuilding a continental A65. our vintage chapter has decided to rebuild one of our engines and now am having a lot of trouble finding the data on clearances.
Pretty simple- you need TCM A-65 Overhaul and Parts manual, p/n X30012.  This manual is $20 and available here

This is the official Continental manual.  You can find all sorts of reprints from Wag Aero, Aircraft Spruce, Ebay, McCurtain Technologies, etc., but this is the latest one straight from the factory. 

Harry 

[Editor's note:  The site has overhaul manuals for all Continental engines, not just the A65] 


Prop Strikes

Went to take a look [at a plane for sale] and did a preliminary check.  The problem is that the owner tells me he had a prop strike when he was trying to hand prop the airplane (prop is toothpicks and chop sticks now)but he claims that because the prop is (was wood) then the engine(A-65) is not damaged in any way.
Prop strikes are a very serious condition, regardless of the engine.  Both Continental and Lycoming have Service Bulletins regarding prop strikes, so it is not a small matter.  Inspecting the engine is more than just checking runout of the flange- bearings can become dislodged, connecting rod bolts can get stretched, the impulse couplings on the mags can engage at too high of an rpm.  Issues which are harder to find are cracks in the gear teeth of the engine drive train.  For example, when the crank suddenly stops, the gear teeth can be jammed together, resulting in a crack in the bottom apex of the gear tooth. 

Overall, it is too simplistic to say that just because it was a wood prop, the prop strike is ok, or that some engines handle prop strikes better.  I have been part of dozens of NTSB accident investigations through the years. It the accident involved an engine with a catastrophic failure, invariably all parties involved would search for evidence of a prop strike. 

Here is a link to the Continental Service Bulletin regarding prop strikes.  Here's the Lycoming Service Bulletin.  Although different
engines, the physics of the prop strike remain the same.  Basically, both engine manufacturers recommend engine teardown and inspection. 

Harry 


More On Oil Pressure

Thank you for sharing your knowledge with the  A-65 community. I have  recently purchased a luscombe with the A-65 engine. I currently have oil pressure that is running 23psi at cruise power with an oil temp of 180 degrees on an 85 degree day. The oil pressure is 10 psi at idle.
I also have to reprime the oil pump after several weeks of no running.  The oil pressure seems very high just after start. It indicates 90+ pounds for the first three minutes after start then slowly comes down. I plan to remove the rear case and inspect the oil pump area and gears. I have several questions if you have time to consider my situation. ( I have read your other response to oil pressure problems on the web site)

What does the high oil pressure at start indicate if anything?

Do I have to remove the engine to remove the rear case?

How do you measure the oil pump bores, gear to wall clearance  and gear  back- lash etc. I have an overhaul manual but the tolerances are not obvious.

Generally speaking, your oil pressure at cruise and idle is not too far off. The reason that your pump loses prime is because there is excessive clearance somewhere in the oil pump system.  This may not mean that there is a significant problem, but it isn't like a new pump. 

A very common "fix" for low idle oil pressure is to install washers under the spring which fits into the oil pressure relief valve.  The idea is that this increases oil pressure in the system.  The fallacy with this, at least in my mind, is that once the relief valve opens, the oil pressure will still default to whatever pressure the pump can generate.  The oil pressure relief is kind of like a pop off valve- when the pressure hits a certain value, the valve opens, and the overall pressure drops to whatever the oil pump system can generate. 

So, spring tension is increased, the pump over pressurizes the system until the valve pops off.  Pump pressure then drops to some low value.  The spring and valve close when the pressure drops.  The pressure then builds up again and the cycle continues.  It doesn't sound like you have exactly this problem, but my point is that I think that washers under the oil pressure relief spring only mask other problems. 

For a cold engine, even on a warm day, 90 psi may not be all that unusual. 50 weight summer grade oil is still pretty thick and it may take a while for it to warm up and flow.  I have seen 100 psi or more on colder mornings with 50 weight oil. 

The oil pump specs are a stack up of tolerances, so there is not exactly an as "as assembled" tolerance.  There will be tolerances for the pump bore, and specs for the backlash of the two pump gears meshing, but no OD spec for the gears to determine an edge clearance.  The thought process is that if the bore is correct, and the backlash is correct, then the overall set of dimensions will, by default, be correct. 

The bore is measured using a special micrometer which is T shaped and has opposing depth probes.  A caliper will provide a ballpark clearance, but will not be accurate.  You need to get your hands on a proper bore micrometer. 

Backlash is measured using feeler gauges or a dial indicator.  The dial indicator held in a fixed position, and one of the gears is held in a fixed position.  The probe from the dial indicator is placed against the face of a gear tooth of the gear to be measured.  The moveable gear is moved until it stops backwards and forwards against the gear being held in a fixed position.  The amount of movement is backlash.  Repeat the process for the opposing gear. 

Backlash can also be measured by inserting feeler gauges between the crowns or highest point of the gear faces.  Insert gauges until the gear no longer moves, and this should be the backlash figure. 

If there is either too much edge clearance between the oil pump gear teeth and the walls of the oil pump pocket in the accessory case, the holes where the oil pump gear shafts pass through the accessory case are worn, or the depth of the oil pump pocket from the base of the well to the top of the cover plate is too great and oil is leaking past, then you will have an oil pressure problem.  It could be a combination of all three problems.  Another remote possibility is that the oil pressure relief valve and valve seat are worn.  Basically, you can't tell until you open the pump up. 

All of the tolerances are in the back pages of the Continental manual, and you have to kind of dig through the numbers.  All of the information is there, though. 

Harry 


Metal in the Oil Screen

HELP:   I changed my oil and found pepper sized metal in the screen.  I have a C90-12F with 2 hrs tach time SMOH. Actual run time about 15  hrs. (taxi and warm up time).    In the rebuild, the case was rebuilt. New crankshaft added, 4 new  millinium cyls, new rods and bolts. new acc case, rebuilt mags, new  oil pump (a lot I can not read in logs) Oil Filter STC, carb rebuilt etc. The overhaul manual says expect metal shavings in 1st oil change but  no big pieces ????????????
The pieces are not big enough to pick up as they all pepper sized and  attract to a magnet. Is this really normal or is there a major issue?  Since I have done a lot of metal work in the hangar, could some of  this been pulled into the engine?

You will get some metal for the first few hours as the rings and cylinders break in.    The look of the metal oil/slurry is kind of silvery and it is not unusual for the oil on the screen to have a slightly grainy feel. Irregular flakes are a reason for concern. . 

But I looked at your pictures, and that is a lot of metal.  I think that you have a problem.  Being that it is ferrous, I’d have to think through what the source may be.  Break-in metal is very fine, not flaky like the pictures. 

Ooops- did I forget to give you a bullet to bite and a swig of whiskey before I gave you the bad news? 

The source of the metal is probably one of the following: 

Whatever part failed is under constant rotation and is literally grinding apart.  If rings failed, the ferrous would be mixed with aluminum bits.  If the crank was snapped in half you might see flakes, but they would likely be larger and have a “smeared” look.  Gears tend to disintegrate in jagged chunks, and the debris would not normally be uniform.  If a cam or follower failed, then the flakes would also be larger and more smeared looking.  I’m willing to bet that the starter clutch has gone bad or an impulse coupling. 
Harry 

Slick Mag Gear Alignment

I have read your articles on Slick Mags trouble shooting, and Inspections. I can't seem to find information on alignment of the rotor gears when reinstalling the top.
There are marks on the small gear in the magneto, and I assume the top needs to be pinned.  Could you help ?

The old 4200 series had the distributor block mounted on the top housing. Molded into the distributor block are tow holes, marked "R" and "L".  On the small rotor gear, which mounts to the rotor shaft, there are teeth marked "R" and "L".  Depending upon the date of manufacture, the small gear may have a line in the gear tooth to clearly identify the R or L tooth. Sometimes the R and L were molded into the gear tooth, which required the assembler to confirm the proper tooth. 

The R and L refer to magneto rotation, not the position of the magneto on the engine.  Generally speaking, all Slick mags rotated in matched sets, i.e., both mags either turned right or both turned left.  There are some exceptions with a couple of Bendix mag applications (Lycoming IGSO-540, GO-480, GO-435, O-435) but the Slick were never applied to these engines. To the best of my knowledge, all Slick mags are paired in turning the same rotation. 

On the magneto data plate, there is a box labeled "ROT" for rotation.  There will an R or L in the box.  Align the corresponding letter on the small drive gear with tab protruding out of the coil.  Use a timing pin or small nail to align the appropriate letter in the distributor block and gear assembly.  Connect the condenser lead to the contact points (ensure that the lead does not touch the housing) and mesh the two halves together. 

Harry 


A65 Hesitiation/Miss

I have a Continental 85 with slick 4001 magnetos. The engine has about 550hrs on it and 180 since a top end overhaul. The engine has not seen a lot of service and has only been sporadically ground run (on mogas) in the past 3 years.
Current problem is a hesitation or miss on acceleration from 1200-1500 rpm. This goes away when the engine is hot. The mags are timed according to the manual (28 and 30). The bottom plugs are new and the top recently clean and gapped. The engine does develop good full power and will idle nicely. I've tried adjusting the mixture, checking for too lean. The mag drop shows a slightly higher drop when running on just left than on just right.

When powered back the engine does not backfire or die.

Any guesses or troubleshooting philosophy for me?

You probably have some blocked bleed holes in the carb.  If you look into the carb throat, you will see a series of holes running vertically in the bore.  As the butterfly opens, more of the holes are exposed.  There is an airbleed circuit which provides the transition from idle to cruise power settings.  I'm pretty sure that this is the problem.  Could be that the throttle shaft is too loose in the carb housing and air is being pulled past the elongated shaft holes.  By the way, I'm assuming that you have a Marvel Schebler MAS carb.  The only fix is to get the carb to a shop to run on a bench. 

I doubt it is the mags.  Mags tend to run poorly across the spectrum of engine performance, or break down under load.  They actually suffer the least problems in the midrange as the electrical load is pretty low and the mag is spinning fast enough to generate decent current.   The carb, however, has separate fuel flow circuits for idle, midrange and cruise.  If the engine stumbles specifically in one of those ranges, especially the midrange, it is probably the carb. 

Check out the Precision Airmotive website, the current makers of your carb.  Go to support, and then click on the MSA carb link.  The info is kind of thin, but backs up my idea a bit.  There is a support number, also.  Call and ask for Al Jesmer and see if he can offer some help.  Al is a friend, and while cranky, knows his stuff.  You can tell him I said he's cranky, but I'll deny saying that he's competent! :-) 

Harry 

Followup

I had written to you some time ago about a homebuilt aircraft I own with a C85 and stromberg that was stumbling/hesitating between 1200-1500 rpm.
I tore down the carb, soaked it in $55 /gal carb cleaner over night, cleaned the jets, checked the integrity of the float assembled, set float height etc, etc and the darn thing still hesitated.

I then started to get an intermittent miss on my engine (discoverd when a friend was going to check me out on my 'new to me' plane). So, I started chasing that around and tore teh carb down one more time.

At this time I borrowed a Marvel carb for troubleshooting.

For the miss I checked the timing of both mags, changed distributors and leads to opposite mag, the miss moved. Meaning it was on the bottom plugs not necessarily a particular mag or harness. I checked all the plugs for spark and was getting a nice fat blue spark when the impulse couplings fired them.

I was a little baffled, so doubled checked everything again by swapping harnesses etc. I finally took the plugs into the shop where I work and checked the plugs on our plug tester. At 100psi pressure, one plug was intermittent and after about 1 minute of testing and cleaning, completely failed. It was a brand new plug i had put in. Go figure.

Now that the miss was sorted out, I put the cleaned again stromberg back on. I discovered that the second time I tore the carb down I must have gotten whatever was causing the hesitation as it accelerated fine.

I did notice that the bottom plugs were getting oily easy and that when I bought the plane it had EM41 plugs in the bottom. REM40 or REM 38 are called for. I swapped out the two most oil fouled plugs for the hotter plugs and my mag drop is barely perceptible. With the REM40's it is about 100 RPM.

I'm just curious, was the plug that caused the stumbling a Unison Autolite plug by any chance?  The early versions used a conductor that would break down after a few minutes of operation. 

In any case, a very difficult problem to find, but I'll make sure that I put long term plug testing into the "deep" troubleshooting as a method to use when everything else fails.

One of the local builders here used the Aero Vee on an A-65 and it provided mixed results.  Basically, it was hard to get it dialed in to work properly across the power band without stumbling.  He traded it off for a Marvel Schebler and his engine runs perfectly! 

A larger airbox will help with stumbling.  It is not so much the inlet area, but the depth below the intake into the carb.  It seems like vertical minimum of 4" is about right and 6" or more is better. 

Thanks for  the feedback on how you solved your problem. 

Harry 


C-85/O-200 Swap

I want to swap my Continental C85-12 to an O-200.
The C-85 and O-200 have different engine mount configurations on the engine case.  Spacers will be required to position the O-200 correctly- usually about 1.5 to 2 inches.  If your airplane is experimental, you can just machine these, if it is certified, there are STC'd parts available.  I have these spacers on my engine and I'll have to measure them and get back to you. 
You don't mention what type of aircraft, but if you have a fuel pump now, the same pump can be fitted to the O-200.  There might be some machining and extra parts depending upon the model of O-200.  If the pump is just needed for takeoff, install an electric pump, just for simplicity. 

The exhaust from the 85 will bolt to the O-200, and he generator from the 85 will work, also.  If you want an alternator, the regulator and associated wiring changes. 

Other than that, your prop will probably need to be re-pitched to make use of the extra horsepower.  Baffling may need to be modified slightly, and various engine control cables may need to re-fitted.  Overall, not a complicated change, but there are a bunch of little details. 

Harry 


Piston Pin Caps

How do you get the piston pin caps out of the pin with out damage? And how do you get them back in?

I tap the caps and pins in and out with a large dowel or a piece of wood, preferably a hardwood like maple.  A small replacement hammer handle works well, or the handle of a small hammer.  The pin can also be tapped out using a deep well socket that is just under the OD size of the pin. 

Harry 


Thread for Case Sealing

[Editor's note:  When the two halves of engine cases are re-assembled, a small piece of thread is placed between the flanges to help the seal.] 
I am currently overhauling an A-65 and trying to find out what is the best thread for the case halves.  I have read the service bulletin and see Continental specifies their own part number.  Is this the best or only option available?

I use whatever Aircraft Spruce lists in their catalog.  I’ve always used the Continental thread or the Spruce thread- never had any problems with either. To be honest, I’m not sure if one thread is better than the other.  You can hardly go wrong using the OEM part number, though. 

Harry 


A65 Cracked Lifter Body

I installed my a-65 and gave it a couple of minutes of ground run, checked for idle mag check ect. Shut her down and checked for obvious leaks. So far so good, perfect. I took her up today to break her in. About twenty minutes into the flight I started smelling oil and noticed the oil pressure starting to slowly drop. looked out the side, and saw oil starting to accumulate on my left landing gear leg. I made a quick landing, taxiing back I notice oil pressure was very low 5 psi maybe? Anyway I pulled the cowl, what I found has totaly dumfounded me. The lifter body housing underneath cylinder #2 was cracked, all around the exhaust pushrod side and through the hole for the stud on the intake side. What the heck could of done this?
P.S. I was down to 2 quarts of oil, cause of the low oil pressure on landing?

The pushrod fits into a cup, and the cup fits into the top of the lifter body on top of the hydraulic unit.  On the O-200, there is a wire ring which holds the cup in place, but on the A-65 there is not. The cup can become dislodged and jam against the pushrod.  The end result is usually a bent pushrod and a broken pushrod housing.   This usually does not result in a big oil loss, though. 

Harry 


RPM Drop with Carb Heat

We fly a 1943 J3C with a Continental A65, TT 2000 hrs. . As always this engine starts very poor when it is hot.
Compression and oil consumption of this engine are good, but we do have a little problem with the carb heat, although baffles and muffler are checked and ok.

When applying carb heat on appch at about 1800 rpm there is a drop of about 300 rpm. Max RPM with carb heat on is only 1800 RPM. During colder temperatures (about 15° celsius two weeks ago instead of 24° today)  the drop of RPM was normal. The spark plugs are black and the exhaust is light brown. I have also observed that the fuel consumption is slightly higher than before and the lower part of the air filter is wet from fuel. To me it seems that the mixture is to rich, although nobody has changed the setting.

When applying carb heat, the mixture effectively becomes more rich.  The heated air expands at a faster rate than the fuel, so there are more fuel molecules than air molecules.  If your mixture was rich, and then carb heat was applied, then the richened effect would intensify.  There are a few reasons for a rich mixture.  Leaking primers are a primary problem.  If the primer leaks, then extra fuel is sucked into the intake.  The primer can be disconnected, and the intake port capped off with a rubber vacuum line cap (available from an auto parts store).  Conduct some test flights to see if the color of the plugs change. 

If the carb float has sunk, the needle valve will stay open too long and flood the intake with fuel.  A very common problem is a leaky needle valve, which usually doesn’t cause the engine to run poorly, but will result in a fuel puddle under the plane when the plane is parked.  A sunk float will result in a lot of fuel under the plane when parked. 

Although rare, some A-65 engines were equipped with a carb with a throttle accelerator pump.  If the pump leaks, the carb will run very rich and the engine will be hard to start. 

Another possibility is mag timing. If the timing is too retarded, the engine will run very rich.  Retarded timing usually helps the engine start, but if it is way off, then it could impede the starting.  Broken impulse coupling springs could cause this problem, also.  What make and model of magnetos are installed on your engine? 

The first thing that I would check, though, would be whether or not the primer is leaking. 

Harry 


Bad RPM Range-Carburetor

I have a continental A75 that I recently just overhauled.  I  also overhauled my NAS3.  During our ground run break in's the  engine runs fine at idle and reaches full static 2250 RPM but  runs absolutely terrible from about 1500-2100.  Infact it will  almost die when transitioning.  Oddly enough the application of  carburetor heat seems to improve the acceleration.  We did  remove and airfilter and that seemed to make the acceleration  worse.  It definately seems to be accelerating lean.  When  rebuilding the carb, we found a 1 5/16 inch venturi and  replaced it with a 1 1/4 inch.  We also installed a rounded  seat and delrin tip needle (no leaks so far!!!!).  We verified  main jet size.  Originally the back suction mixture plate was  removed and wired full rich.  We installed a plate we had  laying around with all associated parts listed in the manual.   Do we have an air bleed restriction?  We definatly dipped the  carb in solution and cleaned it thoroughly.  Any Idea's or  thoughts?
Sounds like one of the airbleed holes which transitions from idle to full throttle is plugged.  If you look into the carb throat, you will see some small holes in the wall.   It could be that you have air leaking past the throttle shaft, too.  Air gets sucked by a loose shaft and leans the mixture. 

The best way to clean the carb body is by an ultrasonic "tub" cleaner.  SIU has a pretty good A&P school, so you might be able to see if they have one on hand.  The other way to clean the carb is to dunk it in a can of Gunk carb cleaner.  The Gunk carb cleaner comes in a one gallon can, smells terrible, but really, really works.  I just cleaned a couple of really rough motorcycle carbs and the before and after is really stunning. 

The problem, though, is that you will have to disassemble your carb to clean out the airbleed circuits.  Do not use wire to clean the holes as scratches, however minute, will make the carb run worse and you can't fix the scratches.  Also, do not try to blow out the airbleed holes with the float installed- the high air pressure can collapse the float. 

Harry 


Power Loss after Maintenance

After performing some maintenance to my C-75, it is no longer developing full power. The engine responds normally when the throttle is pushed to 1900 RPM for run up. Magneto and carb heat drops appear normal. However, when the throttle is pushed in further, RPMs max out at about  1900 and it gets just a bit rough. (Static RPM spec is 2060) Then, after a couple of minutes warming up, RPMs creep down to 1700. If we lean, RPMs increase (sometimes more - near normal, sometimes much less) and the engine gets smoother. So, the engine seems to be running rich.
This started immediately after the following maintenance:
After the above listed maintenance, the plane was no longer developing full power, so we attempted the following:
None of the above had success in solving the problem.
Cleaned the carb (Stromberg NA-S3A1) mixture plates twice. The second time, the engine started working normally. Several full throttle run ups on the ground were good. Then, suddenly, it reverted to the failure. Cleaned the carb mixture plates a third time, but there was no improvement.
All of this is baffling two A&Ps and me.

I took out the carb for an A&P to go through it. However, none of the original maintenance work involved the carburetor.

The other thing I can think off is that maybe the pushrods on cyl 1 were slightly different from each other and maybe we switched them around (even thou we marked them). Would that cause the problem I am experiencing? I noticed the slightest oil trace creeping from the air intake of cylinder 1. Would that be related?

The most important clue that sticks out is that you removed the right magneto.  Is your engine power loss on both mags or just one?  If the power loss is just on the right magneto, then the right magneto timing is wrong. The right magneto must be pinned for LH or Left rotation.  It is very common for the right mag to be pinned for RH.  The timing pin is inserted into the timing hole according to rotation, not placement on the engine.  If the mag is pinned for R rotation, the points can be synchronized to fire at the correct firing point, but the distributor finger is over the wrong tower. Remove the magneto and re-time.  While the mag is removed, check that the impulse coupling spring is wound properly.  There should be about ¾ turn of spring tension to preload the coupling. 

Another possibility is that the ignition harness is wired wrong.  On the left side of the engine, the numbers embossed into the engine case are a bit confusing.  The number for the forward cylinder is positioned in between the cylinders, but positioned towards the rear cylinder.  The rear cylinder number is usually at the back of the engine, hidden by baffling.  It is common to switch the top wires on the left side of a Continental from front to back. 

The pushrods should not make a big difference, but check the valve lash according to the A-65 manual.  It is possible that you have a collapsed lifter, but I would expect the engine to buck pretty badly and the power loss would not be smooth.  A stuck valve would also cause the engine to run pretty rough, also. 

Otherwise, if your rpm problem is within a specific power range, and is the same power loss when running on either the right or left mag, then I would suspect the carburetor.  The carb is a component common to overall engine operation, whereas cylinders, lifters, valves, and mags can be isolated down to a particular area or circuit of the engine.  The carb will cause an overall engine performance problem.

Harry 


High Cylinder Temperatures

Harry,  I just got my 1946 8A flying again.  I put wing tank and a C-90 engine in it but I have high oil temp.  The cylinder temp runs between 325 at low power settings (2150-22500 and 375 at high RPM 2450+.

I have very good baffling and a big enough outlet.  Outside temp has been between 80-90 degrees and the best temp I can get is 215 degrees.  The oil temp drops to 190 in the pattern after let down.

I have opened-up the exit on the bottom of the cowling since the photos were taken and added a lip.

The first thing that I check is to make sure that the gauge is reading accurately.  Water boils at 212 F, so boil some water and drop the oil temp into the boiling water.  The gauge should read in the ballpark of 212F. 

I don’t know much about Luscombes and oil temp problems, so I can’t offer much on the engine/airframe combination.  However, I don’t recall seeing oil coolers on Luscombes.  The guy in the hangar next to me has an 8A, so I’ll take a look under the cowl and see if there are any clues to baffling.  The Cessna 120/140 uses a blast tube on the oil temp probe housing to bring the reading on the gauge into line.  Cessna reasoned that oil temp at the pickup point was not accurate and felt that the heat of oil in the sump was a more accurate measure of temperature.  Some oil sumps also have a ½ baffle that covers the back of the sump and has about a ¼” gap to let air flow through. 

On the engine side, high oil temps are sometimes indicative of worn main bearings, but you would have a noticeable drop in oil pressure.  Possibly, the oil pump is low on output and is having a hard time pulling oil from the sump to pump around the engine.  Maybe the pickup on the sump tube is obstructed.  Usually, adding an oil cooler to an engine with worn bearings or a weak oil pump aggravates the problem.  The cooler has a lot of added friction and the oil pump simply can’t move the oil through it. 

A final thing to check is mag timing.  If the timing is too advanced, the engine can run hot, but you would probably notice higher CHT.  Do you have an EGT gauge?  The temps there should run about 1200-1400F. 

Harry 


Altering An O-200's Power Curve

I am looking at buying a J3 prodject. Frame and wings almost done sans covering. The engine is a 1500 hour 0200 off of a C-150. All I have been able to determine is that the power curve on a stock 0200 is not the best for a cub type a/c. It has bben suggested to change the cam to a C-90 and get the same power curve as a C-90. It seems there is a question as to what lifters you can use and if a carb. jetting change might be needed. If I get this project I may just run it as is till I get to TBO then overhaul it an make the changes then.
I am wondering if you have any thoughts on this. Have you had any experience with converting a 0200 to have a more C-90 power curve?

There has been the wives tale of the C-90 vs O-200 for years.  I strive to base my answers on factual data, and avoid lending credence to the unsubstantiated claims, but there is the possibility that there is some science behind this wives tale. 

Nearly 25 years ago, a veteran Continental rep told me that the C-90 cam was a bit hotter than the O-200 cam.  The reason?  The C-90 was in production when wood props were common, but wood props were not as efficient as metal, therefore the C-90 cam had a bit more aggressive profile to extract a bit more torque to achieve equivalent performance from the wood prop vs the metal prop.  When the O-200 hit production, wood props were not used on production planes, so the cam profile was optimized for the more efficient metal props.  So, while I don't have hard data to work from, the comments from a veteran Continental engineer that I trusted make the premise that the C-90 cam is a bit hotter than the O-200 cam believable. 

There may be an apples to oranges comparison to the C-90 and the O-200 which may appear to be credited to the cam, when, in fact, the cam has no effect. The C-90-8 is a non-electrical engine and the O-200 is usually fitted with a starter, generator, etc.  The -8 engine can weigh as much as 20 lbs less than the C-90-8.  Less weight feels like more power. 

A major hurdle to jump is that the C-90 cam is not a legal installation in the O-200, so you would need to obtain some sort of FAA approval to make it legal.  You will undoubtedly be told that the C-90 cam just drops in, which is true in the mechanical fit sense, but it is not FAA approved. 

Having said that, let's step away from theory and into the real world.  To notice the benefit of the C-90 cam, all things would need to be equal in terms of engine and airframe, and in the Cub world, this rarely happens. Airframe rigging, weight, propeller, engine condition and pitot static system calibration all play a factor in determining comparison performance. A C-90 on a straight, light Cub will perform much better than an O-200 on a heavy, out of rig Cub.  Aircraft trim will also play a factor in Cub performance as the trim is controlled by moving the horizontal tail via a screw jack.  Due to varying aircraft CG and engine thrust line the trim position will change and affect the overall drag of the airframe. 

The underlying theme here is that the C-90 cam may provide some benefit, but either the C-90 or O-200 has ample reserve power to pull a loaded Cub around on a hot summer day.  Build your O-200 light and remove the accessories and you will probably be very satisfied with the performance of your Cub. 

Harry 


Stromberg Mixture Control

I have a J3 'Cubby' with an A65 engine.
The carb has a mixture control on it, but it is wired open, with no mixture control cable.  I am told that this is normal, and a mixture control would " ... not work ...".  It seems to me that the little guy runs rich, and it would be useful, and safer, to have a working mixture control.

The mixture control on the NAS3 carb is largely ineffective.  Most operators have found little to no effect after connecting a cable to adjust the mixture.  I suspect that there is not enough airflow through the mixture circuit to make any difference.  I have only noticed a slight rpm increase at altitudes above 5000 feet, and only then maybe about 75 rpm increase. 

You may be able to get some info from Precision Airmotive, www.precisionairmotive.com <http://www.precisionairmotive.com/> .  Precision is the current owner of the Marvel Schebler carb line, but they really only support the current products.  However, either  Pete or Al in product support may be able to provide a better answer. 

However, there is no harm in connecting a cable to the mixture arm to see if you notice any change. 

Here is a link to the Cessna 120-140 website tech section and it gives an excellent summary of the relative effectiveness and benefits of the Marvel mixture control. 

Harry 


Cylinder Interchangability/Stuck Valve

I've read through your information (several times); it's good stuff!
One question I didn't see answered is mine. I fly a 7EC Champ with a C-90-12F engine. The engine was overhauled about 125 hours ago, using overhauled, rather than new, cylinders (channel-chrome). If I want to have a 'spare' cylinder in my possession, are they interchangeable between the C-series (65, 85 & 90) and, perhaps, the O-200/300 engines?

That is, if I should find, for example, a new-in-the-box cylinder for an O-200/300 will it be useable (and approved) on my C-90?

How 'bout a C-85 cylinder? I presume all new ones come with the piston & rings; will the C-85 piston be 'different'? I think I already know the answer is "yes." Would I be able to use a standard C-90 piston in this cylinder?

I also think I'm experiencing a sticking valve. If the engine hasn't been run for a week or so, it loses rpm about 2-5 minutes after take-off. The tach drops from 2400 to 2200-2250 for just a brief period (15 seconds, up to a worst-case 3 minutes or so), then picks back up and runs fine for the rest of the flight. If it's run frequently, the problem doesn't manifest itself.

An engine guy told me he could fix it one of two ways. Pull the cylinders (we don't know which is troublesome), ream the guides .001", hone the cylinders, install new rings and start over with the break-in. The second method is to fill the gas tanks, fly 'til they're empty, and repeat as necessary until the problem goes away. He suggested continuing to use mineral oil, rather than making a switch to ashless dispersant.

The A-65 and A-75 cylinders are a smaller bore (3.875") than the later 85/90/O-200/C-125/C-145/O-300 (4.062").  The C-85 through O-300 engines all used the same cylinder, the only differences are basically the piston.  The C-90 and O-200 use the same piston, but the 85, C-125, C-145, and O-300 use a piston with a bit more height to the crown. 

Regarding  your stuck valve, it could be a collapsed lifter hydraulic unit, also.  What I'm thinking is that the hydraulic unit is sticky, then eventually warms up and gets inflated with oil and starts working.  Stuck valves usually fail the other direction in that performance worsens as the temperature increases because the fit of the valve to the guide gets tighter. 

Lifters can be fished out of the engine without pulling a cylinder by running a magnet tool down the pushrod tube.  It is easier to pull the cylinder off slightly and then remove the lifter.  Frankly, if you can pull the cylinder off slightly, you may as well pull it all of the way off to freshen it up. 

Although I hate to mention Marvel Mystery Oil as there is no science to prove that it works- although none to prove that it doesn't, either. But, it can't hurt to run some MMO to see if the lifter hydraulic unit frees up.  It probably won't, but MMO is a cheap and easy step in the fix-it process. 

Harry 

Follow-Up

Hi, Harry. Thanks for the reply!
I thought the cylinders for 85 and up were the same. Thanks! I can keep a piston and a set of rings on hand as well, I guess, just in case.

I'm running MMO in the oil (1/2 pint or so) and in the gas (generally auto gas). I put in about 2 ounces per 6 gallon can.

The lifters were rebuilt (whatever that means) at overhaul but what you say seems likely. It does run fine through run-up and takeoff, though. When I get a mile or so out is when the roughness begins. Perhaps the lifter stays 'pumped up' if the engine runs frequently, but loses its oil when it sits too long.

The hard part in all this is diagnosing the problem. Since it runs fine cold, I can't tell which cylinder stays cool. I guess I'll have to install either a CHT or EGT. Since it doesn't have a working mixture, I really don't need either, I think. Maybe a temporary installation would do it. I'll see if I can borrow one.

The lifter is actually an assembly of parts.  The tappet body is the metal housing which holds the hydraulic unit and the pushrod socket cup.  The tappet body is generically referred to as a lifter.  The face of the tappet is ground at overhaul to make it smooth typically is referred to as a rebuilt lifter. 

Harry 

Another Stuck Valve Question

I have a 1946 Tcraft with a Continental C-65 dataplate but C-75 internals.  It has been sitting in the hangar for 3 years, not flown, run, or turned over  at all. Engine has about 100 hours SMOH.
Ran it today, and it really only ran on 3 cylinders. This makes it sound funny but a mag check works out fine. Full power was only 2000 rpm. Climb rate was minimal to say the least.

Anyway, a compression check validated the bad cylinder,  zero compression.  We removed the rocker cover and found the exhaust valve stuck open (probably its position for 3 years?). The valve spring can not overcome the sticktion between the valve stem and the valve guide. How do we fix this?  Do we have to remove the cylinder and all that or is there some way to free up the valve? Would the rope trick push it back in all the way and once movement starts we might be home free?

You might be able to loosen the valve with Marvel mystery oil or other types of penetrating fluid and compressing the valve closed with rope coiled in the combustion chamber.  You might be able to work it free by tapping the valve in and then pushing it out with the rope trick. 

However, my opinion is that the best way to fix this problem 100% is to remove the valve completely and ream the guide.  I'm going to plead some ignorance, though, as I am not sure that the valve can be pushed fully out with the cylinder installed- I've never done it this way!  I usually just take the cylinder off and completely remove the valves, ream the guides, and lap the valves.  It could be that the valve can just be pushed out, the guide reamed and then fish the valve back into place. 

I tend to nuke problems and just repair parts 100%- that is just my personal preference.  It is not entirely unreasonable to tinker with the valve to see if it can be unstuck and returned to service.  It takes me a couple of hours to remove and install a cylinder, but I have done lots of them, so it is not a big deal to me.  The T-craft is a bit more difficult in that the entire exhaust is one piece and needs to be loosened up and dropped, though. 

Harry 

Follow-Up Response:

Anyway, using rope in the cylinder to push the valve closed  and a little  hammer to tap the valve open, and some penetrant and lube to free it up;  pretty soon the valve was working fine. No compression at first, but after flying it for 2 hours compression came right back. Engine performance was  normal immediately.
So, all in all, not a big problem to solve.

I guess I'm too pessimistic about simple fixes!  Sometimes the simple approach is the best. 

Harry 


Hard Hot-Starting

We have a 0-145 that will not start when it is hot.  It will start cold and runs great but will not restart hot.  Removed plugs and still have spark but engin will not restart until cold.
The problem is almost certainly that the O-145 magnetos do not have impulse couplings.  The impulse couplings are spring loaded devices which delay the ignition spark to an optimum point to start the engine and then release with a snap to accelerate the magneto rotor shaft to produce a more intense spark.  The snap of the impulse coupling can be heard when turning the prop over- it will be an audible, mechanical snap or clank noise.  The stock mags on the O-145 are non-impulse coupled Bendix Scintilla SF-4 magnetos set to fire 28 or so odd degrees before top dead center of crankshaft travel.  The optimum point is about 0 degrees. 

If you have a certified aircraft, solving the problem is relatively not easy.  If the engine is on a homebuilt, the solution is more simple due to easier paperwork issues.  A Slick 4373, Lycoming LW12706 spacer, Lycoming 3CTA studs, gaskets, and a Continental 36066 magneto drive gear can be fitted to the left or right magneto position to provide an impulse coupled magneto.  The Slick magneto uses a shielded ignition harness, so shielded plugs need to be mounted to either the top or bottom position of the engine. If the engine is in a certified application, the FAA will need to issue a 337 Field Approval, which is difficult to obtain.  Lycoming did make an impulse gear for the O-145, but I have only seen one of these ever, so they are rare. 

Harry 


28-Volt Alternator for O-200

I have an odd off the wall sort of problem.
My partner and I bought our avionics too soon. In fact, it was before we know what engine we were going to use and we assumed that we would be able to find a 24 volt generator to fit nearly anything that we chose to put in our aircraft.  We chose 24 volt because we always assumed more power was better and if we had a choice, go big.

Well, we ended up with a great deal on zero time rebuilt 0-200 (pickled perfectly for $3,000).  I had just about given up trying to find a 24 volt generator for the 0200 until just this afternoon when  guy a few hangers down said he had one on the 0-200 in his EZ.  I went over to look at it because when I asked if he had a part number I could get off of it he said he didn't have it handy but come look.

Anyway, we got to talking and it was not in a convenient place for me to find a part number (though I did physically see it), then I had to go pick up my son and I lost my chance to look further.  Anyway, this guy is going to be out of town with his hanger locked up until about Christmas.  He swore this was a 24 volt dealie though I cannot remember for sure if he said generator or alternator, (it looked like a black bodied, gear driven generator as opposed to what a standard belt driven alternator looks like). He said something like BnK or B and K or BnC in terms of the manufacturer.

Here's what I need really really badly.  If I can't come up with a 24 volt electrical supply for all of my radios and strobes and gadgets, I'm gonna have to sell them all and replace them with 12-14 volt stuff.  If it was only a radio or two, I could live with it, but everything I have is 28 volt and I got some really great deals on these items that I'm completely unlikely to be able to get again in the 14 volt neighborhood. This mistake has the potential to cost me thousands of dollars and a great deal of time. Do you know of or have you heard of or can you point me to a manufacturer of generators with a name that is something like BnK or BnC (B&K or B&C) that will fit the 0-200 and produce 24 volts.  Or, even better, do you have knowledge of the actual part, part number and or where I could find it?

I've never seen a 28 volt alternator for an O-200, but that doesn't mean that it doesn't exist.  Here is a link to B&C Specialties, http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?17X358218, and their alternator page.  Talk to Bill Bainbridge and see if he can make you a 28 volt alternator- I'm thinking that he can, but ask him. 

Harry 


High Oil Pressure

I just purchased a T-Craft L-2b with an A-75 (I am told not confirmed yet) running an A-65 prop.  I noticed upon delivery of the plane the oil pressure was around 45+ psi.  I put a new gauge in and get 41-42 psi cold or hot (190+ degrees), which lets down a bit when idled.  It has approximately 300 hrs and very good compression. It is also blowing a decent amount of oil out of the breather tube.  My other A-65 in my BC-12 has always had a steady 35 psi and very little oil out of the tube.  I tried to remove the oil pressure relief valve but the cap was very tight and I did not want to force it.  I don't know if someone placed washers in it or not.  I am running 50 weight in it currently.  I know 30-40 pai is normal, but I am not happy with the oil on the belly of the plane.  Any thoughts on the high pressure reading??  Thanks!
Your  oil pressure is certainly on the strong side.  Normal oil pressure at cruise is 30-40 psi, and 10 psi at idle.  My A-65 runs about 35 psi, which is what I consider a good, normal operating pressure.  The oil grade which you are running is good for summer operation and is good for the engine temps which you are reporting. 

Oil blow-by is caused by excessive case pressure or excessive oil splash due to an overfilled crankcase or oil running at a level higher than 4 qts.  A simple start is to unscrew the oil pressure relief valve from the engine and remove any washers.  A correctly operating engine should not require any washers.  The washers are a temporary fix, anyway, as when the oil pressure relief valve opens, the overall pressure is whatever the engine can sustain. Restricting the relief valve only delays the trip point of the valve, so pressure will only be good when the valve is closed.  I suppose that enough washers could be jammed into the oil relief spring so as to completely disable it which would result in no pressure relief and relatively high oil pressure.  I'm not sure what the negative implications of high oil pressure would be in terms of engine lubrication- that is something I would have to put some thought into. 

Another possibility is that you may have good compression, but still have some amount of leakage past the rings.  When conducting a compression check, remove the oil filler cap and listen for air whistling in the sump- there should be little to no air sound.  If the air sound is there, then the rings are leaking, the crankcase is pressurizing and oil mist is being blown out of the engine. 

Related to the cylinders, chrome finished cylinders will leak more oil than plain steel cylinders.  The bore of worn cylinders is often chromed to return the diameter to a standard service size, but the chrome is not "wetable" in the sense that oil sticks to it.  Oil will cling to standard steel surfaces, but tends to run off of chrome surfaces and gets blown out of the engine during combustion.  In this case, the compression may be good, the rings tight, but the oil simply gets blown overboard due to the low wetability of the chrome cylinder surface. 

Another very common problem is the location and type of the oil breather tube.  There is a lot of splash oil in the Continental which collects on the crankcase internals and walls of the crankcase.  The breather outlet is flush to the surface of the case and oil simply gets pumped overboard due to the fan effect of the rotating crankshaft and rods.  If the breather is pointing straight down, then the chance for oil to be pumped out is greater than if the breather tube is pointing aft and slightly upwards.  An even better fix is to solder an extension tube onto the inlet end of the breather to extend the breather pickup deeper into the crankcase and away from the oil on the surface of the engine crankcase.  I use a breather tube with an extended pickup on every single Continental I own and it makes a positive improvement on every single one in terms of oil blowby. 

The following link will take you to a short article with pictures which accurately describes the vent tube modification. http://www.mooneymite.com/maintenance/continentalbreatherfix.htm.

Harry 

Follow-Up

I was able to pull the pressure relief valve, no washers.  The spring was dark colored, (no paint).  I installed a green spring from my spare A-75. The pressure went up to a strong 45 psi from the 40-41 I was experiencing. My A&P said there were several color coded springs.  Should I be looking for another spring, would it affect the pressure in a positive way, (lower)?
I'm not sure if there are color coded springs, although I have a light blue, green and black springs.  I wonder if there are different colors for different models, such as the A-65 uses one color and the O-200 uses another color.  As far as I know, there is only one oil pressure relief spring for the 65 series engine.  You have asked an interesting question, though, so I'm going to work up my chain of smarter monkeys and see what kind of answer they throw back down at me. 

Overall, your relatively high oil pressure could be due to fairly close tolerances between the journals and the bearings.  Maybe there is a restriction in one of the oil galleys.  The oil circulation system is just like the human circulatory system in the sense that if there is an "artery" blocked, then the pressure will increase.  However, unlike humans, what is the real stress of slightly higher oil pressure?  The pump really won't wear, nor will any passages burst.  The only real problem may be oil volume may be restricted and lubrication may be reduced.  I'm wondering if a multi-grade semi-synthetic like Exxon Elite may work better in your engine. I use Elite in my engines and I have never had any problems, other than my oil pressure runs just a tad low at temps above 90F ambient. 

Harry 


Crankshaft End-Play

I have a PA11 homebuilt on floats, with a C90 engine that was completely overhauled by the person who built the airplane, who is now deceased (died of cancer).
The aircraft is working great, it doesn't use hardly any oil, about 1 qt every 12hrs. Oil pressure is great and temperature as well.

The engine has about 60 hours on it, but it seems to be very close to the limit on crankshaft end-play. I am measuring at at about .022 and i am wondering if i should be concerned about this, and what might be causing it with so little time on the engine.

The crankshaft endplay may just be the sum of the tolerances in your engine. I'm not sure if it is a problem with your engine, the sum total of the tolerances on your engine might be at one end of the spectrum. 

I'd have to ask around, but the end play will be controlled by the bearing placement in the engine and the width between the radius' (radii?) on the crankshaft journals- the crank will simply bang end to end as the journals reach their limit of travel against the bearings. 

I'll ask around about the endplay, but in the absence of any negative operating conditions, I'd say it sounds like you have a good motor. 

Harry 


High CHT

I have new Millenium cylinders for my A-65 in my Chief.  I am at times concerned about the CHT.  The cylinders have about 25 hours on them now and I am still running mineral oil.  Before putting a lot of work into my baffling, I was having trouble keeping the CHT from getting below 400F. After the baffling work, my range is typically 340F to 400F.  Cruising at 2150 RPM results in a CHT of 385F or so.
My oil temp is never above 170F.

Anyone had these cooling problems?  Baffling is sealed now very well with all air going down over the cylinders.  Being that the cylinders have only 25 hours on them, should I expect improvement (soon I hope)?

The CHT is a bit on the high side, but to be expected with new cylinders. There is a lot of friction for a period of time while the rings seat to the barrel.  Most engines break in after 25-50 hours and the CHT drops.  The A-65 sometimes takes a bit longer due to the lower rpm vs a comparable O-200 (2400 rpm) or a Lycoming O-320 (2500 rpm).  Higher rpm simply gives more scrapes per minute and the cylinders break in quicker.  I usually run the A-65 a bit hard to get the cylinders to break in. 

Harry 


Typical Oil Consumption

Was wondering what you consider normal oil consumption for a A65 or A75, and what you would consider excessive??? Looking at a bird with 165 hrs on the major, but seems very sooty in the ex stacks.  Don't know about the plugs though,  the owner says1/2 qt per hour consumption.  I think this is to much and probably shows the oil ring not working..
½ quart per hour is high for an A-65.  The cylinders are either glazed or the valve guides are shot and oil is getting sucked into the combustion chamber.  In either case, regardless of hours, the oil consumption should be about a quart every four or five hours at the worst and about 10hrs/qt in the better extremes. 

Determining the limit for oil consumption on an A-65 is difficult.  The manuals that I have do no list any limits at all.  I guess that the underlying theme is that by the time the engine is using a lot of oil, there will be a number of other warning signs like fouled plugs, leakage during compression checks, etc.  Some owners interpret the lack of a high limit as “don’t worry about it.”  Common sense dictates that, despite the lack of a spec, ½ qt/hr is high.  Poll 10 mechanics and the owner and chances are that the only guy comfortable with the consumption is the owner.  The mechanics won’t like the high rate, but if they can’t put their finger on a spec, or they can’t find a compression or leakage issue, then they can’t argue the owner down. 

A compression check will give an indication if the rings or cylinder bore are a problem.  The compression should be low and air should be heard whistling into the oil sump if the rings are bad.  Valve guides are more work as the valve needs to be dropped out of the guide and the guide bore checked- pretty difficult to do on the engine, but not impossible.  Lycoming has a “wobble” check where a dial indicator is positioned against the valve stem and it is wobbled in the guide.  If the valve stem wobbles too much, then the guide is shot.  The problem is that Continental does not have specs for the same sort of check, so it is a bit subjective. 

Harry 


Exhaust Pipe Movement

I have a '47 Cessna 140 with a C-85-12F in her, I just love my little baby.
I have the Blo-Proof exhaust gaskets and stock exhaust pipes. My concern is that when cold when I grab the pipes outside the cowling I'm able to move them just a little (1/8 to1/4 inch) back and forth. Is this nomal for Blo-Proff Gaskets

Is your 140 fitted with Hanlon Wilson exhaust stacks or the original pancake mufflers?  I'm willing to bet that it is the Hanlon Wilson (they are round like coffee cans, whereas the pancake mufflers are kind of rectangular and flat).  The Hanlon Wilsons have a bunch of slip joints which allow the muffler and pipes to move around a bit.  The pancake style is rigid, which is the cause for AD's for frequent inspection.  Because they are stiff, they can't release tension and simply crack over time at the junction where the pipes enter the can. 

The blo-proof gasket should be tight like any other gasket.  Look for movement specifically at the exhaust to cylinder attach point- there should be none.  I've got a Cessna 150 uncowled here with the asbestos filled gaskets and I just gave the exhaust a tug- tight as can be except the tailpipe wiggles at the slip joint. 

Harry 


Mag Timing and Climbing RPM

I have a 46 Taylorcraft with a A65-8 Continental engine.  Max RPM in flight is 2300 with the prop that I have, I cruise at 2150.  I would like to have a little more RPM during climbing.

My mag timing is 30 degrees before top center left and right.  How would changing the timing to 29 right and 32 left affect the engine?

I know it's not legal to remove the restriction in the spider, so I would not do it.  If the restriction was removed how would it affect the engine?

Changing the timing of the mags won't have a noticeable effect on engine rpm.  Changing prop pitch to a flatter, or less pitch, will be the only way to get more rpm. 

I'm not aware of any restriction in the A-65 spider, so that's a new one on me.  Is this something specific to a Taylorcraft? 

Harry: 


O-200 Backfire

I am having a problem with backfire in the exhaust system.  The left side, bank cylinders #2 & 4, is the effected side.  I can see black soot at the muffler baffle near the exhaust end.  I don't see any soot or burn marks at the exhaust flange to muffler attachment.  I am using blow-proof exhaust gaskets.  The cylinders have 190 hours since overhaul and .005 oversize rings and stainless exhaust valves.  The CHT on #2 cylinder has never been over 400 degrees, but the exhaust side of all cylinders shows possible high temp reddening of the paint in the area of the exhaust port.  The mag drop is about 100 rpms on the right and 150 on the left mag.
The backfire was almost undetected 20 hours of flight time ago, but has progressively gotten worse to the point that it backfires a lot into the muffler at low rpm now. The EGT on the #2 cylinder is still around 1200-1300 degrees.  The backfire is a low rpm below 1,000 but Saturday the backfire got so bad that I just shut it down.  I have a feeling that there is a hole blown in the new left muffler and gas is getting into the baffle and out around the exhaust stack near the bottom of the baffle and that I may have burned exhaust valves.  It is apparent that unburned fuel is getting into the muffler before exploding. The top plugs were checked a few hours ago and looked a light tan color. The same two cylinders were bore-scoped and appeared not to have any exhaust burn marks.  The mechanic said they looked okay.  The compression on the cylinders was 76/80 at that time.  That was just 8-10 hours ago and after the first popping was noticed.  I could use a suggestion.  I was told a plug or megneto could cause the problem or unburned fuel at low rpm.

I would check a couple of things.  First, ensure that the ignition leads running to the top left cylinders have not been mixed up fore and aft.  This is a very common problem as the number embossed in the case to reference cylinder #4 is actually closer to the rear cylinder, #2.  The embossed number for cylinder #2 is behind the baffling and not readily visible when in the cowling of most airplanes.  In other words, #4 cylinder is the forward cylinder, #2 is the rear and the ignition leads need to be routed accordingly.  The engine will actually run with one lead misrouted, but will run terrible on the mag firing the misrouted leads. 

Next, a more likely problem, is a sticking valve or hydraulic lifter on either cylinder #2 or #4.  A compression check is the first thing to do to detect any obvious problems with burned valves.  If no leakage is detected, then check the condition of the spark plugs to see how fouled or how clean they are.  If there is an obvious difference between the plug condition between the two cylinders then I would start to troubleshoot #2 as you think that there is a problem there.  Sticking valves are kind of hard to find until they literally jam in the valve guide and become clearly obvious. When the backfiring starts, do a mag check left to right- if there is a stuck valve, then the engine will run poorly on both mags.  If just one mag, lead or plug is bad, then you can isolate to one side or the other. 

The solution to the stuck valve is to remove the valve from the guide, ream the guide and re-install.  This can be done without removing the cylinder from the engine, your mechanic should be able to accomplish this. 

Harry 

Follow-up

Thanks.  I believe you are correct.  I have checked the sparkplug leads. They are correct.  I am very confident it is a stuck valve on either #2 or #4 cyl.  I had a mechanic look at it in PuebloCO.  I was told they found nothing wrong.  I have to go out and look for myself as I checked it just hours prior to them checking it and it was popping.  They said they tightened up the intake manifold tubes on that side and there was no trouble.  I will have to see it to believe it.  I also believe your suggestion about dropping the valves and reaming them is the cheapest way to get the stuck valves taken care of.  What do you think about Marvel Mystery Oil?  I was told to try that.  Does it work?
Marvel Mystery oil doesn't hurt, although once the valve sticks, there is no option other than reaming the valve guides.  MMO won't fix big problems and is more of a preventative measure (although there is no proof that MMO provides any benefit). 

Harry 


Popping Sound/Backfiring

I know you are very busy but you are the man to go to with engine problems. I am looking at a cub with a C-65 with 850 since major. The AI is now doing the annual.

Problem is after a couple of minutes of running if you did a runup to do a mag check it has this popping sound. They check all the intake tubes and rubbers and clamps. The AI was baffled and talked to some friends and they came away with this suggestion. It could be a blockage in the exhaust system and try changing the muffler. I seem to think it is most likely a stuck valve as it acts up after a couple of minutes of running not at the start. Hopefully the muffler will be changed today. If that isn't it how do you go about locating a stuck valve and can it be properly repaired with the jug in place. The other thought was that it might be an exhaust leak at the header to jug flange but supposedly that was checked.

If you have a stuck valve or collapsed hydraulic unit, then the problem would be the same when either magneto is selected or when the engine is running on both mags- the valve is a common component to the cylinder whereas the spark plugs can be isolated..  If the popping sound is isolated to one mag or the other, then it is probably ignition system related.  You problem sounds very much like a stuck valve.

Isolating a sticking valve takes some work.  A cold cylinder check is the quickest method.  If the valve is open then combustion does not occur in the cylinder and the affected cylinder will be cooler than the rest.  There is an expensive Snap On cold cylinder detection tool or you could use an infared thermometer.  The infared thermometer is kind of gun shaped like a timing light and is pointed at heat sources and measures relative heat. This type of tool is used in manufacturing or can be bought fairly inexpensively.  Some times, a cold cylinder can be detected by hand. 

If no cold cylinder tool is available or the cold cylinder cannot be detected, the only way to find a sticking valve is by hit and miss.  Select a cylinder, drop out the valves, ream the guides, and monitor the results. 

There could be a blockage in the muffler, but I wouldn't think  that would cause backfiring.  A blockage usually results in low rpm due to the restriction.  Loose baffles should be entirely obvious when the muffler is removed- the baffles will literally be rattling around in the can. 

Harry 


Slick Mag Rotation

A transcribe of some data from Charlie Lasher about his STC to put a C-85 in a Champ...

"Use either a C85-8 or C85-12. If a -12 is installed without starter of generator, install Continental aluminum cover plates over the accessory case drive pads. The conversion does not include an electrical system. Bendix mags will fit. Slick mags only turn in one direction; the converter supplied by Slick will cause interference"

Isn't the rotation determined by which hole you put the timing pin?  Is he talking about the tach drive or the earlier "throw-a-ways" ? Is it possible to use Bendix either rotation so that a conversion from a dash 8 to a dash 12 is possible. If that is the case. I would think that Slicks would fill the bill as well. or is the drive gears have to be changed

The Slick mag uses many parts which are identical between LH and RH mags, but Slick magnetos, by design, only turn one direction.  When the cam slot is cut into the rotor shaft, it is biased to turn either RH or LH, depending upon application.  The rotation cannot be changed as the cam slot cannot be re-oriented.  Other rotation limiting features are the orientation for the impulse coupling keyway, the impulse coupling, and the placement of the impulse coupling stop pin. 

Bendix mags are a bit different- sort of.  The Bendix magneto rotation can be changed from right to left by reorienting the cam, moving the impulse stop pin, installing an appropriate impulse coupling, and timing the internals for the appropriate rotation.  The problem is that the depth of magneto engagement between the -8 and -12 engines is different, so the mag frames would not work and would need to be replaced.  The biggest problem is that there is no approved process for changing the rotation of Bendix mags. The data plate cannot be legally changed, but various LH and RH parts can be installed under the correct data plate (as long as the parts under the data plate equal the approved combination of parts). 

In short, the -8 requires RH mags and the -12 requires LH mags, and the only practical way to get to that configuration is to buy the magnetos correct for the engine model.  Converting existing mags is not practical nor FAA approved. 

Regarding the Slick conversion on Continental engines:  The -8 and -12 engines have different accessory cases with different depths for magneto engagement.  Simplistically, the -8 has a shallow case depth and the -12 has a deep case depth.  The shallow case requires some sort of spacer to provide room for the impulse coupling.  The original Slick K4521 conversion for the -8 engines used spacers between the mag and the accessory cast to provide the depth for the impulse coupling.  The later Slick K4344 kits used mags with a longer frame neck which eliminated the spacer.  The early K4521 kits also required the use of the Continental 36066 drive gear, whereas the later K4334 kit included a gear made by Slick which eliminated the need for the 36066 gear.

In any case, the Slick mags are shorter than the Bendix, so there should never be an interference problem with any conversion. 

I'm going to install a C-85-12 with no electrical using the Lasher STC on my Champ, so I'll let you know if there are any fit problems. 

Harry 


RPM Drop As Engine Heats Up

C-85-12f with cylinders just overhauled and new main & rod bearings.  When the engine is cold, it gets 2300 rpm static, but the warmer the engine gets, the the more it drops. after the oil temp hits 160 degrees it will only turn around 2200 static.   tach was checked, no cht gauge on board, no carb heat connected.  Also, the engine feels a bit tight to turn the prop by hand after it has heated up.  Have you ever encountered a similar problem before ? or have any suggestions.


thank

Yes, I have encountered this problem before and it was because undersize bearings were used with a standard crank.  The standard crank journals are larger than the bore in an undersize bearing.  The engine heats up and the parts get tight.  If any of the bearing part numbers were followed by -M10 or M05, then the bearings are undersize.  Another possibility is if the crankshaft was ground by an automotive shop.  The journal radius used by aircraft is different than automotive.  An automotive grind will cause the bearing to pinch in the journal. 

Other than that, remove the magnetos and re-time to the engine.  Both mags should be set up for left rotation and timed to 26 degrees or so before TDC. If the mags are mistimed, then the engine would get too hot and lose rpm. 

Harry 

Follow-Up

Thanks for the fast reply harry, I took a look at my build sheet on the engine and came up with the following:
The engine had 300 hrs ttsn, and I overhauled it simply because of age, corrosion was not a problem.  Crank is still standard( not ground), the new bearings are also standard, cylinders were oversized ..010 with os pistons and rings.  The only point i can think of where tight fit may be a problem , would be in the valves.  all valve to guide fits were reamed out to the minimum- .003 for exhaust and .001 for intakes,, I'm wondering if its possible for this to tighten up too much after heated?.  The engine is still at 1 hour tso and has not been broken in yet and i dont want to damage it but would running it at 1000 rpm for a  couple hours help wear it in if it simply was tight valves?  One other option is it could simply be a main bearing out of place... which i know is never a good thing.   I'll try retiming the mags though tonight.

If the valves were sticking, then the engine would be making a heck of a racket.  The combustion would be firing back into the intake or exhaust and the engine would really be bucking. 

The taper shaft bearings have a tendency to slip if the case bore and bearing OD fits are too great.  The bearings for the flange shaft should have a couple of split thrust washers which fit into a machined groove in the front of the case.  Sometimes the thrust washer can slip. 

The rings should not be a problem.  Sometimes chrome rings wind up in chromed cylinder bores and the friction tears the cylinders up.  But, chrome rings only come in standard bore sizes, so you should be ok if the cylinders are oversize. 

What was your oil pressure?  It should be about 30-35 at that rpm. 

I would physically remove the mags and re-time them to the engine.  The contact points may open at the correct firing point, but the distributor finger may be on the wrong tower.  Pull the mags and go through the timing process, making sure that both mags are set up for LH rotation. 

Fuel-wise, there is a chance that the engine is starving for fuel or the fuel system is not ported correctly.  Take the cap off of the airframe gas tank and see if the power continues to drop off. 

One more idea as this just happened to me recently- Is your carb heat control creeping out when the engine is running?  I had this happen with my Champ and it drove me nuts trying to figure out why the engine suddenly started running rich and losing power.  The carb heat control wire had simply lost its friction and would creep out when the engine was running and richen the engine up due to excessive carb heat. 

Anyway, let me know what you find. 

Harry 


Motor Mount Adaptability

I'm now looking at a KR2 with a C65 engine which means hand-propping <frown>. The external looks prettygood (in the picture) and should be getting some interior pics and answers to lots of other questions soon. I do like having the Continental motor. Do you happen to know if the motor mount for a C65 will work with a C85 or 0200? I'd like to work towards the engine with a starter and more HP if possible.

The motor mount for the A-65 and C85 series is the same in that conical rubber bushings are used.  As such, the overall dimensions from the engine mount lugs on the engine to the prop flange shaft remain the same.  The C-90-12, -14, 16 and O-200 have different mounts and the lugs are set further forward on the engine case.  These engines can be mounted on the A-65 mount but require about a 2" spacer to position the prop flange in the same location as the A-65.  the C-85-12 will be your best choice for a low-hassle installation. 

Harry 


Duralube

Hi Harry,  Is it safe to use Duralube in my C85 engine?

The engine manufacturer's have detailed service bulletins for standard aviation oil, but offer no guidance on aftermarket oil additives.  I do know that oils with Teflon as a component suffer a common problem.  The Teflon flakes do not tend to remain suspended in the oil in proportional amounts and the flakes tend to "flock" and bunch up.  Probably not a big problem in airplane engines due to the wide tolerances, but there is no science backing up any of these additives except what is provided by the companies selling the additive. 

Oil additives have been around for decades and decades, but I have yet to see a consensus or any conclusive report that provides any evidence of specific benefits (except reports provided by the makers of the additive product)
.
Bottom line- with no conclusive science to back up the additives, I have no idea if they work, help or harm the engine. 

Harry 


Swapping Rods

Terrific and informative site. At Oshkosh this year I wasn't able to get an answer from any of the engine folks (including rebuilders) as to what the difference is between C-85 and O-200 rods. I had an engine failure on takeoff from my 1200 ft strip and basically destroyed the Champ. I am rebuilding it as a homebuilt and would like to use the C85 rods with the 0-200 crank I bought. I know the STC requires the 0-200 rods and am not sure as to why. Appreciate any followup information. I would like to use a C90 cam as I am told it will also produce extra horsepower. Do you agree? I have an 0-200 cam and an almost new C85 and would like to be re-assured this is a good and safe way to go. Appreciate your advice and thank you in advance.
The Continental A-65 through IO-360 rods all have the same main journal to connecting rod pin spacing.  However, there are significant differences in the structural strength and alloys used in the various rods.  A primary difference is that the C-85 rod has a wider end where the piston pin passes through.  The webbing flare which transitions from the main rod casting to the piston pin journal is not as wide as the O-200.  I suspect that, due to the narrower piston pin journal, that the center of gravity of the O-200 rod is in a different location than the C-85 rod.  The difference in the center of gravity may have some effect on the loading of the reciprocating group. 

I am not sure why O-200 rods are required, but that is what the STC requires, and there must be some sort of engineering reasoning.  Given that your engine is going into a homebuilt, you do have the personal option to experiment and use alternate parts.  I will see if I can get a bit more clarification on this topic, though. 

The C-90 cam has a slightly different profile, but I'm not positive that you will notice a significant benefit, at least in a relatively stock engine. The C-90 cam wives tale has been floating around since the Goodyear racing days when the C-85/90/O-200 based racers were just experimenting with finding more power.  The C-90 cam was optimized to provide torque with a wood prop, and when a short metal prop was fitted, the engine ran with a bit more power. 

Harry 

Follow-Up

Finally someone with no BS info. It caused me to look at the wrist pin area to find the difference between an  0-200 and a C-85 rod. I don't have an 0-200 rod but I have a set of pistons  and find that the there is a big difference in the width between the wrist  pin bosses such that I don't see how you could use a C85 piston with the 0-200 rod. That is unless around .200" slop (side to side) is OK. Nowhere do I find any reference however to using the 85 rods when the C85 pistons are  used with the 0-200 crank. Thanks for the info on the cams. Would it be your


recommendation to stay with the 85 cam when I do the conversion or go to the "more rpm" 0-200?

The bottom line on modifying engines boils down to your mechanical aptitude and personal patience.  If you want to fly more than you want to work on your engine or spend time troubleshooting potential problems cause by experimental mods, then leave it bone stock.  Stock works and is proven. 

If you are a risk taker and understand that there may be more maintenance or time spent tweaking the engine, feel free to experiment.  My hangar is very well equipped and I have a pretty big storeroom of parts at my disposal.  I can remove, teardown, reassemble and reinstall a little Continental in one or two days time.  An average homebuilder will probably take a month to accomplish the same task. 

In concept, though, the O-200 cam should drop into the C-85 case.  If you are using an O-200 crank, rods, and pistons then you will basically have an O-200 in a C-85 case.  I doubt that there is much difference between the two cams in the long run. 

Harry 


Engine Overhaul Period

I am a fairly new pilot (non-mechanic) looking to purchase an amateur built plane. I have found a Zenair CH200 with the following engine specs (as outlined by the owner) and I was wondering if anything sounds suspect:


---------------------------------
Cont.0200A Engine 5-6 gph, 100 hp
729 STOH, overhauled cylinders(Leggat aviation),new pistons  2400 SMOH
Comp.at last anual(oct.3 2005)73/80,70/80,68/80,68/80.
oil consumption 1L/15 hrs (Shell 15w50)
900 TTAF
------------------------------
What is the TBO time on a Cont.0200A?  Does this sound reasonable that there is 2400 SMOH?

Any help you could offer a non-mechanic would be great.  I am not basing my decision on your answers (I will have it inspected) but I was wondering if I should look further into this one or take off running the other way.

Continental Service Information Letter SIL98-9A provides the guidelines for engine overhaul.  Here's the link: http://www.tcmlink.com/pdf2/SIL98-9A.pdf

Continental recommends that the O-200 be overhauled at 1800 hours or every 12 years, whichever occurs first.  However, these are just guidelines and are not considered mandatory by the FAA.  As long as the engine shows no outward indications of performance degradation, in concept, it could be operated indefinitely without an overhaul.  It is very common for O-200 engines to have a top overhaul at about 1100 hours, and then soldier on for another 1000 hours until the top end needs to be re-worked.  I have seem more than one O-200 go on for 5000 hours before a complete overhaul.  It is usually when the second set of cylinders runs out that the O-200 gets completely overhauled.  However, there is no definite time frame which dictates how long the top end will run before it needs overhaul- 1000 to 1200 hours is just a common amount of hours where the cylinders are likely to require service.  Some cylinders go less, some go more- it just all depends on the results of the yearly condition inspection 

The compression for the engine below is average.  68/80 is pushing the lower limit and anything in the 70's is in the middle.  Oil consumption is also average, about 1 qt every 6-8 hours. 

So what does this mean?  There are many items which determine engine condition, but, on the surface, the condition looks routine and it should be reasonable to expect to see another 200-500 hours of service.  There is no definite answer, though.  The life remaining in the engine just depends upon compression, oil consumption, oil pressure, and external leakage. 

Harry 


C-85 Pistons into O-200 Follow-up

I have a Varieze and am in the process of a top overhaul and am wanting to use C-85 pistons.  Can you explain to me the mod that is needed to be done on them to be used in the O-200?
I've read the 30 degrees at 1/2 " but what is the angle and distance measured from ? My father is a machinist and has a shop so the mod shouldnt be any trouble but I want to make sure its done correct.

Also with the increased compression, can the ignition still be kept at 30 or so? or does it need to be retarded a bit?

The bevel is at the top of the piston crown at the OD- if you have a piston to look at the bevel is obvious.  The width of the bevel varies from piston to piston for some reason.  When the C-85 piston is used with the O-200 crank, the piston travels further up into the combustion chamber.  The angle at which the inner dome of the combustion chamber intersects the cylinder barrel can vary, and the standard piston may bump into this intersection. So, the bevel needs to be about ¼” wide with about a 30-45 degree angle to provide clearance when the piston is near the top of the combustion chamber. However, this figure is not exact as the tolerances vary from cylinder castings and pistons.  You may have to tweak the chamfer a bit if tolerances get tight.  However, a ¼” wide taper gets you pretty close. 

Standard ignition timing can be used or bumping it to 30 degrees doesn’t hurt.  Basically, fly the engine, and bump the timing incrementally to find the point where power is increased and CHT is acceptable.  There is a crossover point where power goes flat and CHT continues to increase as timing is advanced.  Typically, most O-200 engines using magnetos are not advanced much past 32 degrees. 

Harry 


Problems Splitting A65 Crankcase

Hello, I am doing a complete overhaul of an A65 and am down to the bare crankcase.  I am having trouble trying to break the seal and splitting the case. Any suggestions? I am surely not going to start prying, as I do not want to damage the mating surfaces.
Make sure that you have removed all of the bolts and nuts around the case spine.  There is a 9/16" nut on the bottom of the engine between the #1 and #3 cylinders which I sometimes miss. 

The case halves may be kind of glued together, also.  Dab some MEK or lacquer thinner along the spine to try to get it to leech in between the case halves to loosen up any sealants.  Use a piece of wood to tap against the tops of the through studs and against the relief holes in the rear of the case.  It really should not take much effort to get the case halves to split open.  In fact, even if the case are sealed with Permatex, they should kind of fall apart once all of the hardware is removed. 

My bet is that you may have missed the nut between #1 and #3, though.  I've done it a few times. 

Harry 


A65 Prop Removal

Thanks for such a great website regarding small Continental engines.  Great resource.
Do you know where one can obtain a tool for removing a metal prop from a 65-A (I believe).  There is a slot there but I cannot budge it, so far.

I think that you are talking about the prop hub.  These can be a real problem to remove.    Here is a link to some info:
http://www.luscombesilvaire.info/endowment/pop_topics/ctsc.htm. 

This link shows in detail how to remove the hub. Unfortunately, there are no ready made tools, but solutions can be fabricated in the field. 

Harry 


Bendix SF4 Magnetos

I have located a couple of A-65 engines removed from Taylorcrafts that the owner was upgrading to higher horsepower engines. They are A-65-8 with the Bendix SF4 mags, 400 stoh, $2000 each.
Are the engines with non-impulse mags more difficult to start? Is this engine a good choice for the Fly Baby from a weight standpoint?

The SF4 magnetos are pretty good magnetos if they are in good repair, but they will start an engine differently than impulse coupled mags. 

The non-impulse SF4 is timed to fire 28 degrees before the piston reaches the Top Dead Center position of the upward power stroke of the crankshaft. As such, if the rotating inertia of the engine is not fast enough, the engine will want to turn backwards if combustion overrides the forward velocity of the crankshaft.  This is especially noticeable with wood props as they are lighter and have less rotating inertia.  Another issue is that, when the engine is hot, the optimum spark timing is about TDC.

So, to answer your question, the SFR mags are pretty good units, but the starting technique needs to be aggressive to swing the engine fast enough to produce a hot spark and keep the inertia of the crank up.  Just plan to physically swing the prop with vigor and you won't have any problems.  Slick makes an upgrade kit with impulse coupled mags, gears, harness and plugs for about $1200, so there are options. 

Magnetos aside, the basic price for the A-65 doesn't sound too bad in today's terms.  Where else can you buy anything remotely capable of powering an airplane the size of the Fly Baby for two grand? 

Harry 


Pushrod Tube Leaks

My C85-12, never a paragon of oil consumption, is starting to leave some streaks on the outside of the cowling.  It's tough to chase them down, but it appears to be coming from the area around the bottom of the rightside aft cylinder. That's the only point on the engine where there is visible crud...there's "oil mist" on other places, noticeable when I wipe a finger on it, but this is the most likely-appearing slot.
This is the cylinder I pulled when I first bought this airplane, and I did have trouble with the clamps and whatnot for the boots.

My guess is, from other comments I've heard, that the pushrod tubes are leaking. I've also heard that Continental has a new type of pushrod tube out.  Have you heard anything about them?

I realize I'm still going to have to pull the cylinder to get the old tubes out, but while I'm at it, what more should I be doing?  Is there any other procedures I should do, as long as I'm pulling it?  This is the cylinder that got the "modern' valves ten years ago.  I remember a gasket at the base of the cylinder, should that get replaced, too?

Finally...what specialized tools do I need, and where should I get them?  I don't even have my own set of cylinder wrenches (borrowed them for the last thing) and figure I'd better get my own.  Is there a specialized tool for those boot clamps?

Continental has a new pushrod tube, but it is kind of pricey.  I don't have the exact price, but I seem to recall $300/cylinder for the change.Basically, the tubes have seal which is loaded by a spring at the base.  The engine needs to be converted to new bolt-on castings which accept the tubeassembly.  In the back of my mind, I think that there may be the need to doa mod to the cylinder, as well.  I'll get some more info for you.  I'm going to be in Ohio doing Airvan demos and visiting Hartzell, so it may besometime this coming weekend. 

Let's discuss the stock pushrod tubes.  These actually work quite well, butover time the swaged end in the cylinder head loses its grip and the end in the rubber boot gets ovaled out and the boot loses its seal.  The stock tubes are fairly inexpensive.  Once again, I'm not sure of the exact cost, but 6 bucks or so each sticks in my head.  I have the special tool which swages the tube into the cylinder head which I'd be happy to loan to you,also. 

The boot clamps require a ring style hose clamp pliers which can be found at Sears.  This is pretty much the only tool for the job.  Get your cylinder base wrenches from Aircraft Tool and Supply or one of the other tool companies which advertise in Trade-A-Wreck.  The base wrench tools are all pretty average quality, but are relatively cheap at 60 to 80 bucks for a set.  You really only need two wrenches for the C-85- 1/2" and 9/16" if you just need the specific tools.  The large 5/8" in the set is used for 470/520 engines and the small 7/16" in the set is used for the A-65. 

Ok, moving on to what to do when the cylinders are removed.  Hoo-boy- lots of different directions there.  If the engine is running well with no outward problems, and the engine is not a showpiece, I'd recommend that you don't do a whole lot other than remove and replace.  If it ain't broke, don't break it by trying to fix it. 

Personally, I rarely pull a cylinder and not pull the valves or hone the cylinders.  But, for the amateur, doing this type of work may cause more problems than are solved by less work.  Once again, if it ain't broke... 

Actually, pulling the valves is dirt simple and the only tools required are a fence post and a claw hammer- no kidding!  However, I will leave you hanging to puzzle how those tools will work as I need to get ready for a trip tomorrow.  I will send you a more detailed e-mail later this week. 

Harry 


EGT Probe Location

Hi, I have a Continental A65-12 on  a Jodel D112, I am going to fit an EGT probe on one exhaust stub - any suggestions as to which cylinder is likely to run leanest?

Traditionally, the EGT probe is installed on the right rear cylinder.  It is placed furthest back, and has the most restricted cooling, so has the potential for being the hottest cylinder.  In reality, this may not be the leanest cylinder.  The leanest cylinder may be different in climb and cruise configurations, also.  To be scientific, one would have to measure the temps of each cylinder to accurately determine the lean one.  However, a good starting point is the most rearward cylinder. 

Variable Oil Pressure Rise Rate

I have a Champ with C-85-8 engine with 300 hrs. When its cold the oil pressure comes up very slowly but when hot it comes up very fast. Pressure at operating temp. is between 35 and 40 lbs. I use Phillips 15W-50. Is this normal?
This sounds entirely normal.  Despite the fact that the oil is multi-viscosity, it still has to be warmed to an operating temperature for the viscosity to stabilize.  So, when it is cold, the oil is a bit thicker and oil pressure takes a bit of time to pump through the system and register.  When warm, the oil flows more easily and registers more quickly. Your oil pressure sounds good, so I wouldn't worry. 

Case Leaks

Harry, I've enjoyed reading the information you've posted. It helped me a lot since I purchased my Piper Vagabond with A-75 and did a top overhaul.

Now that I'm flying it, I notice a few oil leaks (very slight seepage actually) around some case bolts.

Is there an approved sealant I can put on the washer/bolt to stop these leaks?

Welcome to the Continental Leak Club!  Leaks occur at these locations due to hardware which is tightened down on painted surfaces, or re-used hardware, especially washers, which may no longer be flat and have distorted a bit due to compression. 

I usually lap the surfaces of the washers and nuts prior to installation using valve grinding compound and a flat surface.  Kitchen counters and bathroom sink tops are great for flat surfaces, but the consequences of unauthorized use are often dire. 

Sealant, like Permatex, under the mating surfaces is not such a good idea as this material can loosen over time and the securing hardware can lose torque (although Continental does approve Permatex for the case halve mating surfaces).  You can try a bead of sealant around the edges of the hardware, but I've not had much success with this, either.  Many times the oil is simply leaking down the case through bolt threads, so some low strength Loctite can fill the voids and help to reduce the leakage. 

You should re-torque the case through bolts and hold down nuts after a few hours, too.  After initial run in, the engine stretches a bit, so snugging, but not overtorquing, the hardware is a good idea. 

Harry 

[The questioner posted a follow-up] 

Thanks for the info Harry. I wasn't too sure about using permatex, but I thought I'd ask.  My other idea is a little medium weight TightSeal. As far as losing the torque, I'm hoping the pal nut will do its job. In any case, it's easy to re-check them occasionally. Just re-read my note, and I forgot to mention that it's the top through bolt right above and behind prop shaft. It's only leaking on the nut side. I'll lap that washer, try some TightSeal, and let you know how it goes.

I got a good chuckle about unauthorized use of kitchen and/or bathroom countertops.

TiteSeal will also work.  The little Continental likes to seep oil, so be patient in trying to fix leaks. 

Yeah, the countertop thing is a real chuckle.  My wife doesn't realize that I got yelled at a lot as a kid, so I just take whatever she dishes out.  I tried to sell her on the idea that her yelling at me counts as "us" time, but that hasn't worked, so far.  Of course, she hits me with logic like, "Why don't you buy your own four foot section of countertop to work on?" That would be too easy and would defeat the greater satisfaction of "getting around the system".  Whatever that system might be... 

Another resource on stopping leaks is Bill Pancake of the Aeronca group. The last e-mail I have for Bill is w8spk@verizon.net.  Bill is more detailed than I am about fixing, well, details.  Bill's restorations are utterly immaculate and my airplanes are not museum quality.  I'll live with an oil drip and I think Bill is more thoughtful about fixing such things.  Another resource in the Cub world is Clyde Smith, but I can't seem to find his e-mail.  Both Clyde and Bill are friends of mine, so feel free to drop my name. 

Harry 


A65 Oil Pressure Slide

Hope you can help me with my continental A-65.  The engine has 50 hours SMOH (at least that's what the log book indicates) and one hour since I replaced the crankcase cover and the oil pump gears.  I replaced the cover, gears, oil pressure relief spring and plunger because of low oil pressure (low 20's psi) and upon inspection found both case and gears were worn.

The replacement crankcase cover appeared to not have any flaws or signs of wear and the gears, spring and plunger are new and I lapped the plunger.

I'm using 40 wt. mineral oil.

At start-up I have almost 40 lbs.  After an hour of flying, my oil temp of 140 (50 degree day) my oil pressure was back down in the low 20's.  At idle it is 10 psi.  I put in the three washers behind the oil pressure relief spring and I've tied the old stand-by of banging my head on the hanger floor but still have low oil pressure.

The engine runs and sounds great (I only get 2150 rpm but I'm fairly sure it's because it's propped wrong with too much pitch).

What else could cause the low oil pressure?  At what pressure is it not safe to run the engine?

If you read through my other posts, the oil pump and accessory case are a chronic problem on the A-65. 

The pumping capability of the A-65 oil pump is based not only on the condition of the gears, but the edge clearance between the gears and any leakage which may occur at the gear shaft holes.  So, replacing just the gears may not solve the problem.  If you are doing this kind of work you undoubtedly have a manual.  Check to make sure that the bore of the oil pump pockets is to spec and that the diameter of the gear shaft holes are the spec.  It could be that when the engine warms up, the case expands a bit, the oil pump gear loses the viscous seal at the edge of the gear and pumping pressure drops.  Putting washers under the springs does nothing to improve oil pressure.  If the pump is already unable to produce pressure due to leakage, then increasing the demand for pressure will not improve the end results.  Once the pump achieves a pressure high enough to overcome the spring tension, the overall pressure will drop to whatever the pump can maintain or the fit of the bearings will maintain. 

The pump cover plate can be finicky to set up.  The cover plate sometimes needs to be re-torqued or re-positioned.  Of course, this presumes that the bores and gears are 100%. 

Another very likely culprit is worn main bearings.  Tight tolerances will restrict the oil flow a bit and loose tolerances will result in low pressure.  If the clearances of the bearings become too great, no oil pump will be able to deliver enough pressure.  A sign of main bearing wear is decent oil pressure at start, but then falls off as the oil thins.  Usually, low pressure due to worn main bearings is also accompanied by high oil temps.  If the oil can't flow back to the sump fast enough to dissipate heat, then the oil temp will rise.  This effect will vary from engine to engine, and may not be noticeable in temperatures lower than 70F. 

Oil pressure should run 30/40 psi at cruise (max 60 psi) and about 10 psi at idle. 

One last think to check is the oil pressure gauge.   Connect another gauge to see if the pressure results are similar.  If so, then your engine is telling you it is sick and needs service.  The accessory case is a likely culprit and there are not many easy options for repair.  Drake Air out of Tulsa is about the only shop which will attempt weld repairs to rebore the A-65 case- 800-542-6899. 

Harry 


Adding a Starter to a C-90

Owner would like to install a starter on an Aeronca with a C-90. Is there an STC available?  He may accept a starter without the total electrical system.

Is the engine a -8 or -12?  There are no starters for a -8 engine, but you can get a SkyTec starter for the -12.  The starter will work off of a battery and you can probably get 6-8 reliable starts from a 25 amp aircraft battery before having to re-charge.  The number of starts varies depending upon temperature and battery capacity, but for most practical pea patch flying you can just top off the battery daily via a trickle charger hooked up to a quick disconnect lead. 

Check out www.skytecair.comfor info on starters for small Continentals. 

Harry 


Replacing a Rotax Two-Stroke with a Continental

I have a project that sugests a rotax 582, I'm looking for weights on these smaller continentals as I would like to stay away from the 2 cycles.
Where can I find the weights, continentals web site only shows spec. on 0-200 and up.

I know, I need a better project. Have any suggestions besides that.

The lightest of the Continental engines will probably weight twice as much as the 582.  The A-65 weighs 170lbs and the O200 is about 190lbs or so. 

You can find all of the info you need at the FAA Type Certificate Data website.  Just type in the engine model in the box and then keep clicking until you
get to a PDF file with all of the info.  Just read through the data and you will find weight, horsepower, bore, stroke, etc. 

If you are looking for a four stroke to replace the 582, you will probably need a 912, a Jabiru or a VW to keep the weight and balance right.  The good news is that there are plenty of lightweight four stroke engines available. Check at the KitPlanes website for their manufacturer directory. 

Harry 


A65-9 Starter Conversion

I have a -6/-9 starter conversion. does any one have a parts break down on the hummer starter? What would this be worth? I have all of the parts ,including an elect starter, the cones for the mags.
The A-65 parts and overhaul manual has the breakdown for the -9 series engine and starter.  It is hard telling what this is worth as the price depends mostly one the condition of the parts.  A swag would be about $400-$500 for parts requiring overhaul, which is about the cost of a starter and mag gears for a comparable O-200 set up.  Given that these parts are kind of rare, maybe about a $1000 if everything is there and in good shape. Basically, a set of oddball parts that needs to find the right buyer. 

Harry 


C-85 Runs Rough

[I apparently have lost the details of the original question...but it's pretty apparent from Harry's answer.  RJW] 
It kind of sounds like your engine has a sticking valve or sticking valve lifter hydraulic assembly.  These conditions would affect the engine at any rpm and would affect overall engine operation. 

To elaborate, here is my thought process on troubleshooting: 

However, the hydraulic unit can become sticky or simply collapse and fail to pump up to take up the valve lash.  When this happens, the valve does not open or does not open completely and the engine runs rough.


There is a leakdown check for the hydraulic lifters.  Clean the assembly thoroughly, and then pump it up while immersed in Stoddard solvent.  Set the hydraulic assembly aside and check it in 5 minutes- the lifter should still be pumped up.  If it has collapsed and won't hold static pressure, then it needs to be replaced.


For more information on sticking valves complete with pictures, here is a link: 
http://www.sacskyranch.com/eng176.htm

Harry 


Ignition Shielding Cans on Normal Category Airplanes

I need to use two of the Ercoupe shielding cans, from Fresno Air Parts, on the top two front spark plugs on a J-4Cub.
Can you tell me the best way to document this instilation to satisfy the FAA.

I don't have the answer on the cans.  If these are original parts, they were built at time when the approval process was not like it is today.  In other words, the FAA did not require as much detail, if any, for approving these parts for installation and some parts were just installed and became part of the airplane with no real approval..  If these parts were manufactured by Fresno, then there is probably no FAA approval. 

Sometimes, the parts have a an FAA-PMA stamp which provides for blanket approval.  Most ignition harnesses fall into this category- there is no specific p/n for the harness in the Type Certificate for a Slick harness to fit an A-65, for example.  Slick has their own, stand alone, FAA-PMA which can be proven by the Slick application manual. 

The challenge, first, is to determine whether or not the cans are FAA-PMA approved.  If not, then the trail will probably go cold. 

Harry 


A-65 Airbox

Thanks so much for that great guide! This is my first aero engine and it is going onto my Pietenpol which is still being built. I bought an A65 with 130h SMOH with carb, prop hub, and two 4251 magnetos. It came off a Cub that is going up to an 80 to fly with skis. It did not come with the airbox or the mag drive gears.

Is there anything magical about the airbox that would make it unacceptable to fabricate an airbox that did the same thing? Or do you know of any sources for these.

And lastly, unless I am mistaken, by reading your guide and another source or two it seems I am looking at $1,100 for two mag drive gears?  I noticed that Aircraftspruce sells a magneto kit for the A65 for $1200ish that includes the drive gears. While these mags are fine, it seems that the mag kit is a better deal. Problem is it just makes no sense that the gears sell for $1,100 but the mags and gears sell for $1,200. Am I way off on this?

Nothing special about the airbox except that you want to roughly approximate the plenum volume of the stock intake.  If the intake length is too short, or the vertical depth from the intake of the carb to the floor of the airbox is too shallow then the carb may run erratically because the airflow does not have enough time to de-turbulate (to make up a word).  If you approximate the volumes and geometry of the Cub or Aeronca airboxes, then you can't go wrong. 

The 4251 magnetos won't work on the A-65 as they turn the wrong direction, and, no, the rotation cannot be reversed.  The  Slick K-4334-40 kit comes complete with gears, so the 4251 mags can be used as cores towards that kit. The loose gears can be pricey and $1100 is not unusual for a pair of new gears.  Used gears can run about half that cost, but not all gears for the A-65 are the same.  The Bendix, Eismann and Slick mags all use different gears, so when shopping it is imperative to match the correct gear with the correct mag combination.  The easiest, no problem method is to buy the K-4334-40 kit. 

Harry 


A65s and the B&C Starter

Hope you are well. I'm looking at a KR2 with a C-65 engine and previously  understood that starters are not possible. However, B&C Specialty sent me a note saying their starter would work if the right accessory case was used (see below). If B&C  is not pulling my leg, is there a simple way to know what accessory case they may  be referring? I'm gonna put in a question back to B&C and to the owner and engine builder to see what they say.

But you're the "man", so I wanted to throw this issue at you. Truth or fiction on the C-65? Not having the starter won't deter me from buying the plane... but it would  be neat to know if B&C are correct and how to do it (especially with the $$ cost of  their starters).

Hi Ben, 

I think that the B&C starter will only work with the -12 accessory case, which will not fit the A-65 without some modifications.  All of it is possible, but it will be a bunch of work and extra parts.  There is a -9 case, but I am not sure if the B&C starter will fit.  The -9 is a relatively rare part, which adds a quirky part to a fairly straightforward engine.  The -9 and -12 don't use the same starter, but I am not positive that the fits are different (or are the same). 

Generally speaking, I am still unaware of a simple method to put a starter on an A-65. 

Harry 


O-200 to C90 Conversion

I have a chance to buy a wood spar J-3 project that comes with a runout 0-200. Problem is, Univair's STC for the O-200 in a Cub is only allowed in the metal spar wing models. Therefore I am wondering: 1) if it is possible to convert the 0-200 to a C-90 (which is approved for all Cubs via the TCDS) and 2) get a new data plate from Continental for the C-90.

It is not possible to convert the O-200 to a C-90- there are too many detail differences and I can't imagine that the FAA would allow it.  Continental will also never issue a new data plate.   If you can find the correct used or rebuildable case and data plate for a C-90 engine, you might be able to scavenge the correct parts from the O-200 to build up an engine. 

Harry 


Wind-Driven Generator

I came up with an idea - I'm sure not original - about using a motorcycle alternator strung under the fuselage. There are some expensive "aircraft" systems, but I bet I can make something with the motorcycle alt and a small quality prop attached.  I saw today that they make 30-40 amp motorcycle alternators and full kits with regulators, etc.,. I know a guy who put one in a HAPI VW case and it powers everything he needs (COM, mode-c) with only 10amps.
Ever see anyone do this? I figure I could test it driving in the car with a volt/amp meter and light. After attaching, I could create a nice fiberglass cover to dress it up and channel the air.

Thoughts?

You mean something like this

Yeah, another idea that has been done through the years.  A couple of basic problems with wind driven alternators- drag and consistent voltage output through the airframe speed range. 

Typically, the alternator is tuned for max output when in cruise.  However, when the airplane is at pattern speed, the alternator has no output as it is turning too slowly. 

Drag is an issue, too.  The alternator has to be a pretty good size and the prop can provide a lot of drag.  I had a torpedo shaped wind driven alternator on my old Stinson 105 and it cut the airspeed by 5mph and made a pretty loud whirring noise when it ran. 

If you start searching on the internet, you will find that there have been quite a number of home brewed wind driven alternators.  I figure that they are a less than complete solution because I don't see all that many installed on planes at airshows like Sun n Fun and Oshkosh.  There is a certain validation of ideas via numbers.. 

My solution to electrics has been a battery and a trickle charger.  A motorcycle sized battery will run most electrics for a days worth of flying and then can be charged overnight via a charge.  Just run a quick disconnect umbilical cord between the battery and the charger. 

Harry 


Checking Out an Inactive Engine

Hi Harry, Just found this websight and it is full of great info. I just purchased a nice project 7ec champ with C-90-12. There is no logs and the owner had passed away, the tack shows about 2300 hrs and the presumption is that the engine was majored at 1800 hrs and now has 500 hrs on it. The engine looks nice with no oil leaks ect. My question is should I pull the engine down completely and have a look or could I just pull a cyl or two and look inside. I would like to major it and start a new log book but I am price sensitive. Also I should say that the engine probably has not been run for 5-10 years, another thing is that the project has a brand new prop which makes me wonder if the old one was bent??
If the engine is to be used on a certified aircraft, the lack of logbooks will cause a problem.  The inspecting mechanic will need some way to reference hours, AD compliance and to enter various airworthiness endorsements for the annual inspection.  Sometimes hours can be estimated and the work can continue on an "on condition" basis, or basically an hours unknown but the engine is inspected for basic health criteria.  New logbooks can be generated by a teardown inspection and overhaul. 

If this engine were to be used on a homebuilt, I would probably just do an inspection of the cylinder bores via a borescope or by pulling a cylinder off for inspection.  If there is a question about the prop strike, then conduct a prop flange runout inspection according to the Continental manual. After the inspections, run the engine "on condition" and just keep tabs on the compression, oil consumption and keep up to date on all applicable AD's. A sick engine provides a lot of clues in terms of compression and oil consumption.  If the operation seems normal, just start a log book documenting hours and condition from the time placed into service and motor on. 

Harry 


O-200 Crankshaft in a C-85

Is there an STC or a place I can find instructions on putting an 0200 crank into a C-85 case with all the accessories  (pistons, rods...) I have a c-85 case that has a runout crank( .004 slop and 1 journal is .001 too small) it in and I am trying to find the least expensive way to get my motor up and working again. the cyc have good compression and only about 200-400 hours on each.I want to use as much in my case that I currently have as everything is fairly low time (everything but crank) and my accessory case was rebuilt in 97 also with new studs and STCSE154ch which is new oversize oil pump impellers.
So my preference would be to be able to just put an  0200 crank in what I have and move on with life, is this possible/recommended?

Aircraft Specialties, 800-826-9252, has an STC for the O-200 crank conversion.  Basically, this is your only option for a crank replacement if a C-85 crank can’t be located.  All of the feedback I receive is that there is no downside to the O-200 crank (except the cost).

If you are experimental, you can install any O-200 crank and O-200 pistons to approximate the STC without the paperwork.  You can use the C-85 pistons, but you will need to machine a ¼” chamfer around the top of the piston crown for clearance in the top of the combustion chamber.  The O-200 crank has a bit more throw than the C-85 and the C-85 pistons are a bit taller from the crown to the piston wrist pin.  The C-85 pistons will give you about 5 more hp, but need to be chamfered for the clearance issue.

Harry


Crankshaft Oil Seal Leaks

I have an O-200 in a Varieze and the crankshaft oil seal is leaking.  I replaced it with a split seal and it didn't fix the leak.  When I installed the new seal I noticed that the ends of the seal didn't mate up very well. In fact, when I finished the installation I inspected the split with my bore scope and found that there was a .020-.030 gap.  It appears that there is some difference in the density of the material that forms the outer circumference of the seal and the inner lip material.  When I closed the seal in my hands so that the thicker part of the seal was contacting, I could see that the area of the lip material still had a gap.  I was hoping that when installed it would close the gap but it did not.
The seal was made by Superior.  Is there a better seal?  Can I trim the thicker part of the seal to eliminate the gap?  Apply contact cement to the gap to seal it better?  Any suggestions?

Yes, I have read Continental Service Bulletin M76-4.  Didn't really help with this problem.

The problem may not be the seal.  The OD of the area in the crankcase where the seal mounts may be oversize from 60 years of seal removals.  The crank to seal contact area may be undersize on the crank for the same reason. Sometimes the crank develops groves at the contact area and the seal leaks. If I get a seal that leaks I install it with about 1/8” to ¼” of the seal face showing so that it is not completely seated.  This puts the seal edge in an area which may not be as worn.  Another thing to check is that the send of the seal lip is mated to the crank surface.  Take your thumbs and press around the center of the seal and you can sometimes feel it snap into place and the lip will contact the crank better.

Other than Superior, there are TCM factory seals.

Harry


Misfire/RPM Loss After Takeoff

I have a Cessna 150 with an O-200A (licence built rolls Royce). About 18 months ago the aircraft developed a misfire on the climb out from takeoff  The misfire appears to get worse in the summer and improve in colder weather. It is normally a "smooth" misfire - it feels like one cylinder is dropping out. There is a significant increase in vibration. It only occurs after takeoff, I cannot repeat the problem in a full power climb from the cruise, nor can I repeat it on the ground, however in summer it goes almost every time on climb out. Typically it starts about a minute after lift off at a few hundred feet, although it has on rare occasions started to misfire on the takeoff roll. I normally get an indicated 2400rpm static, rising to 2500 on the takeoff roll and maintaining 2500 in the climb. When the misfire starts, RPM typically drops to 2300 and the climb rate drops by around 200fpm. When it clears, the RPM immediately recovers to 2500. Switching magnetos while it is running rough only causes the expected RPM reduction, it makes no difference to the roughness. Leaning the mixture generally makes little difference. Pulling the carb heat out does make the engine run even rougher, but unlike with carb ice it doesn't clear, it just continues to run rougher until you put the carb heat back in, at which point it carries on running as roughly as before you pulled it out. However, throttling back slightly to reduce the RPM generally allows the engine to recover after a few seconds - thereafter you can usually go back to full power to continue the climb without a problem.
On very rare occasions (typically very warm days), the rough running has become worse than this with a much larger drop in RPM and severe general roughness although it has never quit completely. On each occasion, closing the throttle slightly has allowed it to recover as described above. These may be a bit spurious - I'm not sure if these "atypical" episodes have been the same problem, or have been combined with carb ice or similar which the aircraft is quite prone to.

At the time it was thought to be a sticking valve (the engine had apparently had a history of a sticking valve problem some years earlier). The cylinders were due for an overhaul, so I had them all replaced with Superior Millennium, however this made no long term difference (it did seem better during the break-in time of the new cylinders though, during which I believe it was run on straight 80 oil). The carburettor has been overhauled, then replaced with a new unit, still no effect. The mags, ignition harness and plugs have also been replaced with brand new units with no success. The aircraft has had 2 annual inspections during this period so things like the air filters have also been replaced. Nothing else has been found wrong, everything seems secure (inlet pipes, exhaust system etc). We have done fuel flow checks from the gascolator-carburettor hose. The system has delivered 200% of the maximum fuel drain required by the carb for more than 10 minutes, even with the tail strapped down to put the aircraft in the climbing attitude and with the fuel tanks running close to empty. The flow rate remained steady throughout the test.

The only pattern I can see other than the temperature dependence is that the problem has appeared to be worse since switching to a new maintenance organisation, and they have switched from W80 oil to W100 oil. My previous maintenance organisation told me they used W80 because of the previous sticking valve history. Having switched back to W80 oil myself the problem seemed to be getting slightly better on each subsequent takeoff, although it is still there at present.

The only parts which we have not replaced which I can see could be a possible cause of this problem are the hydraulic valve lifters. I have found various references around the internet to people experiencing similar symptoms which have been found to be a lifter either collapsing or pumping up. Having already spent a lot of money trying to fix this over a long period of time, I was looking for some advice before spending even morereplacing the lifters.

Any advice or help which you could offer me would be very gratefully received.

Before I even got past the few lines of the second paragraph, I suspected that your problem might be the hydraulic lifters.  The hydraulic units commonly cause the problem which you have described.  Over time, the hydraulic units will stick and simply not open the valve completely and the result is an rpm loss.

You can perform a leakdown check of the lifters by pumping them up with solvent.  The lifter should maintain pressure over a period of five minutes.  If not, then that hydraulic unit needs to be replaced.  However, this test is not entirely perfect in detecting a bad HU- it just sorts out the obviously bad parts from good parts.  A HU which passes the test can also stick over a period of time.

Continental specifies that the hydraulic units are to be replaced 100% at every engine overhaul, but it is not unusual to re-use these units over a period of several overhauls.  The problem is that eventually the hydraulic units will fail.

Given that you have replaced virtually everything else on the engine which could cause this problem, it is reasonable to assume that the hydraulic units will need to be replaced.

Harry


Exhaust Valve Hissing

Harry,  I have a c75 in a 1941 J4 Cub with no electrical system. I have noticed recently that when turning the engine over slowly by hand that I get 3 good tight blades and the 4th is soft with a hiss into the exhaust on the left exhaust. The engine starts and runs fine with no noticeable power loss. Compression checked fine on last annual (30 hours ago). Does this sound like an exhaust valve beginning to burn? Any suggestions would be greatly appreciated..
Yep, that sure sounds like the early signs of an exhaust leak.  You could give it another compression check to see if you hear air hissing into the exhaust port.  It is probably better to fix this problem early on as opposed to waiting for it to get worse.

Harry


Low Compression when Cold

I bought a C-85-12 with 785 SMOH.  Did a cold compression check (engine has been sitting since 2004) and all I got was 20/80 on three cylinders and 30/80 on the fourth.The A&P did not use that special orifice required by Continental.The guy I bought the engine from says The check Must be done with a hot engine using the special orifice and the numbers will be in the seventies.Your thoughts on this are highly appreciated.
A cold cylinder check will yield the least positive results of a differential compression check.  Compounding the problem is the fact that the engine has been sitting for three years and valves and rings will simply not be seating as well as they could had the engine been run.  It may not be possible to perform an accurate compression check until the engine is run.

A compression check is actually a "leakdown test" which is used to check the integrity of the seals of the combustion chamber, namely the rings and the valves.  Continental Service Bulletin SB03-3 completely details the specifics of the test and how to define the upper and lower limits.

Harry

[RJW Note:  When the A&P does the annual on my Fly Baby, we test the compression cold and it comes out in the mid-70s (e.g., very good).  HOWEVER, this is on an active airplane.  The engine referred to above has been sitting for a while.]


High Time O-200/Operating Ranges

I am looking at buying a Zenith CH200 at the moment. It has an O200A Cont engine and I have a few questions about the engine.  The engine has 740 hours STOH and 2400 hours SMOH
  1. When I took it for a test flight I was getting about 35PSI oil pressure.Is this standard on this type of engine
  2. 2400 hours seems like a lot of time to me. In your experience do you think that this engine would have much life left to offer or would it be needing a major overhaul in the near future? I understand that with engines nothing is every certain and it may keep going for 500 hrs or for 5hrs but you opinion would be much appreciated
  3. What is the red line of this engine and what RPM should you be using for cruise power setting?
35 psi is a normal range for oil pressure for the O-200 with 18 psi or so for low end at idle.  Sometimes a worn engine will make good cruise oil pressure, but almost nothing at idle.
2400 hours is high time for an O-200. The recommended TBO is 1800 hours, so this engine is operating in excess of the design limits which more or less guarantee troublefree operation.  Many times, the top end, or the cylinders of the O-200 are overhauled at 1200 hours or so, and the bottom end is left alone.  It is very common for an O-200 to operate well beyond TBO in this case as the cylinders will run for another 1300 hours or so with little or no effort.  I owned an O-200 with 3600 hours which had a top overhaul at 2100 hours.  The engine was pretty thrashed out when overhauled, though, so running it beyond TBO cost more to overhaul in the long run.

There is no way to apply a crystal ball to your engine to determine how long it will last.  The engine condition is what it is, and routine inspections will provide the clues to engine health.  If the compression is good, the oil pressure is good and there is no indication that the engine is making metal, then it can be run indefinitely.  There is no regulation which demands that an engine be torn down at the recommended TBO.  Common sense prevails, though, and a higher time engine just needs more frequent inspection intervals to monitor the health of the engine.

The manufacturer's redline is 2750 rpm and normal cruise is usually 2600 rpm and lower (although there are no rpm restrictions up to 2750 rpm).

The key to evaluating this engine airframe combination is to simply look at the condition as it exists.  If the engine is clean and runs well, then the high hours may not be a factor.  It basically boils down to if the airplane appears to be worth the value of the asking price at the time it is inspected.  Forecasting the reliability into the future is a near impossibility, so focus on what it is at the time of purchase.

Harry


A-65 Storage/Impuse Magnetos

I have a zero time Continental 65 with rebuilt Bendix non-impulse mags.  I am putting it into a Fisher Flying Products Dakota Hawk within the next year(have to finish building the Hawk)  The engine is sitting in my heated(65 degrees on the thermostat), and dehumidified basement, with oil in the system, and dessicant plugs in place.  I have a couple of questions for you:
It is probably going to be one year before the whole thing is hauled out of my basement and the next phase begins, fuel flow tests, weight and balance checks, final inspections, engine run-ups, and then flight testing. Do I need to do anything further to prevent "corrosion" or whatever in the engine that is sitting idle?  I do periodically squirt a few drops of oil into each cylinder and turn the crank over a fraction of a turn.

Everyone is telling me that I have to get impulse coupled mags, either one or two.  Apparently the newer versions of the Slick mag product line are much better than the old ones so probably I would get a Slick product if I do this.  What are your thoughts on whether I should get just one mag rather than two, and if you agree with just one, which side does it go on if it matters.

If I get just one Slick, I probably would keep the swapped out Bendix as a "spare".  If I go to two Slicks, I probably would try to sell the Bendix mags.  Is there any market for these, and if so, what would you guess they are worth?

Here is a link to the Continental Service Bulletin which details engine preservation for storage.

Regarding the mags, here is the summary:

Any magneto works, so long as it is in good repair and adjusted properly. Non-impulse magnetos require that the prop be swung vigorously to make sure that a hot spark is produced and the engine rotates fast enough to get the crankshaft to continue to rotate in a forward direction.  If the prop is not swung fast enough, then the engine can "kickback" or fire and reverse direction due to the lack of forward acceleration to keep the crank moving forward to overcome the ignition cycle.

Impulse coupling are spring loaded devices which latch and hold the magneto rotor shaft to delay magneto firing to an optimum starting point while the crankshaft is turning.  When the impulse coupling unlatches, the magneto rotor shaft is accelerated and produces a hot spark, but delayed to a point to prevent kickback during the starting cycle.

The primary reason for using non-impulse magnetos is cost.  From the practical operational standpoint, impulse coupled magnetos are the only way to go.

It is possible to install one impulse magneto, but the relative cost of installing a Slick K4334-40 ignition kit with two impulse magnetos is not much more that scrounging up all of the parts separately.  The K4334 includes everything:  New mags (not rebuilt), new harness, new magneto drive gears, new ignition harness, new spark plugs, and gaskets.  This ignition kit completely eliminates any concern about starting, serviceability and reliability.  Two impulse magnetos mean that both magnetos are producing a starting spark, not just one.  Also, there is a slight operational issue in that the non-impulse mag must be turned off during start to prevent kickback.  Remember, the first spark wins, so the non-impulse mag can still cause the engine to kickback during start when paired with an non-impulse magneto.

Slick offers a core refund and a rebate for purchasing a kit.  Check with suppliers like Aircraft Spruce for the latest deals.

Harry


O-200 Performance Enhancement

I have a stock 1970 C-150K and was wondering what performance enhancements would improve it's performance. I would like to keep it in the Normal/Utility category. We are operating the airplane out of DenverCO.
There are really no approved methods to improve performance on an FAA certified O-200- it is what it is for certified applications.  Even in homebuilts, there is a limited range of reliable improvements which will yield only about 8-12 hp increase.

About the only improvement for climb performance would be to pitch your prop for climb performance, although cruise would suffer.  The O-320 conversion is popular for high altitude regions, but this is a costly conversion.  It is a more cost effective upgrade to buy a Cessna 172 and reduce the payload for altitude performance.

Harry


Crankshaft Seal Replacement

Harry:  I have a 1976 C-150 with an 0-200A.  The engine runs great but recently has developed an oil leak, of some amount, that I believe is coming from the crankshaft oil seal behind the prop.  I am not positive this is where the oil leak is, but highly suspect it as the culprit. Any suggestions on how best to replace the split oil seal?  The engine has about 5300TT and roughly 900 SMOH.
No big science to the seal- it is a moderate pain to remove and re-install.  The old seal can be pierced with an awl or screwdriver.  I usually poke a hole in it and then start collapsing the seal inward using a set of needle nose pliers.  It helps to remove the prop to do the work, although it is not necessary.  But, you will find the prop to be largely in the way while you work.

Installing the new seal takes patience.  There is an inner spring which must have the ends connected to one another and then positioned into the inner flange of the seal.  You will find that a couple of pairs of skinny, long, needle nose pliers with 45 degree bends at the tip does the job well.

Once the spring is looped and secured into the seal, press around the outer edge of the seal with your thumbs or using a tool handle.  Just press around the OD of the seal fairly evenly.  I usually do not seat the seal flush with the case.  I position the outer face of the seal about 1/8" to 1/4" out so that the inner lip of the seal ( the part that contacts the crank) rides on a "new" part of the crank.  The seal area usually has wear ridges, so installing the new seal to ride just outside of this area usually provides good results.  Once the seal is positioned, work the inner seal area with your thumbs to ensure that the sealing edge is seated inwards and square to the face of the seal.

Without pictures, all of the above is a bit hard to visualize, but once you get the parts in your hands, you will see how it works.

Regarding the oil leak, it could be from a number of areas.  The best way to find a leak is to completely wash the engine down with solvent, run the engine, and then push back into a darkened hangar.  Put a black light into your corded shop light (available at most Home Depot stores) and shine on the engine in a darkened hangar.  Oil leaks will show up as dark lines on the case.

Harry


Adding Electrical System to an A65

I am considering purchase of a taylorcraft bc65 because it was the type of plane my dad used to fly.  I do not really want to hand prop it.  Can this bird be set up for electric start by an A&P?
Currently, there is no way to put an electrical system on an A-65.  The A-65 has no provision at all on the accessory case for starters, generators, etc. The A-65 has been in production for 75 years and there is still no method to adapt electrics to the engine.

The Taylorcraft can be converted to an engine with electrics, but it is an involved project to upgrade up to Model 19 status.  Struts and motor mount must be changed, not to mention the engine and change of pitch to the prop. Not an easy or inexpensive process.

Handpropping is not a hard thing to do, one just has to take care when starting the engine to make sure that the wheels are chocked or the tail is tied down.  Impulse coupled magnetos, such as the Slick K4334 kit are a must for consistently safe starting.

If the goal is an inexpensive plane with a starter and electrical system, the Cessna 150 offers the same realm of low cost ownership as a T-craft, but it is just not as glamorous.

Harry


Acceleration Problem

I would like to ask your advice on a sudden problem I have had with my C85-12f.  It is outfitted with a stromberg NA-S3A1.
This aircraft has recently undergone restoration and has seven trouble free hours on it since the carb was rebuilt.  I had a successful flight (engine ran great!) on Saturday.  During start up on Sunday, she wouldn't idle.  Idle screw was adjusted nearly a turn out until she ran OK.  But during acceleration, I noticed a pronounced miss around 1200 rpm.  But only during throttle advance.  Idle screw adjustment has improved it slightly but it is still there.  Slightly unsettling to say the least.  The only thing I did to the aircraft between Saturday and Sunday was put fuel in it.  I have the carb off to give it a cleaning; I'm thinking small foreign body here.  Other than that I thought I would solicit your advice.I would greatly appreciate any help you could offer.

The problem is almost certainly that one of the holes in the carb throat which provides the transition for air/fuel from idle to full throttle.  It is probably just a bit of fuzz or a small contaminant- it does not take much to cause a problem.   I've attached a photo of the carb throat and transition holes for reference.

Here is how to NOT fix this problem: Do not stick a small wire into the holes.  You run the risk of packing the obstruction even tighter or scoring the passage.  Even slight imperfections in these orifices will affect the carb performance.

Do not try to blow out the holes with compressed air from an aircompressor.  Shooting compressed air into the throat can create a negative pressure in the carb bowl and collapse the float.  I've seen this a hundred times.

Air can be used, but the carb really needs to be split to keep the float from being damaged.  Another good way to remove the blockage is by dropping the affected part into an ultrasonic cleaning tank.  This is kind of a specialized piece of equipment, but it does the job.

Sometimes carb cleaner can be shot into the small holes to blow the contaminant back into the carb bowl.  Kind of hit and miss, but this can work.

Of course, I'm assuming that the fuel system is not causing a problem.  Is this carb on a homebuilt or certified plane?  Homebuilts are notorious for fuel venting and acceleration issues which starve the carb of fuel. However, if the problem is in a specific range, it is probably a blocked transition hole.

Harry


RPM Hunting

I have just imported a Wittman Tailwind from the states with an O-200 fitted with Slick 4201 and Marvel S Carbie. The plane does 140 knots at 2750 rpm. Statict is around 2180 rpm. One early morning I flew in very calm air, around the 2800rpm for about 2 minutes and decided to slow down. As I closed the throttle very slowly, she started hunting around the 2600rpm mark. I immediately pulled the carb heater and added a bit a throttle and all ok again. I then reduced through to 2200rpm , all still good and landed. After much deliberation, my friends and I decided it was carb ice. Anyway, flew some more a few days later and regularly after take-off, I felt the engine missing about as we reach 500 feet and 2500 rpm. And then a defnite missing started happening between 2500 and 2600rpm, I switched the mag to left (little ruf with normal drop) but on the right mag the engine lost lots of revs and run rough-rough - I thought it was going to quit, so quickly back onto both mags.
Now, to date I've removed both mags and had them checked by the magneto shop at Archerfield - found a dead capacitor on one mag, and gave both a good check on the bench, My Lame then installed both mags onto the engine (*LH rotation with tower on number and Engine TDC etc). We set timing to 28 degrees BTDC on both. Leads are new and looking good - plugs were all tested on LAME's plug tester - found intermittent spark plug and replaced with a new one. Also removed tappet covers and looked at valve movement - looks all good) Flew again yesterday afternoon and all looks good. I get to 2750 no problem, but when I switch mags left is good (50rpm drop) right goes rough again) below 2400 rpm, both mags are fine - the mag check shows 50 and 75 rpm dropp respectively at 2400rpm or lower - CHT around 425 and egt around 1300 mark - Oil around 200 degrees and Oil Press around 30 PSI.

Only anomally on this engine which I dont like, is the inlet manifold has been welded all-over - the inlet hoses (all 8) are brand new. I have not opened the carbie - have drained the tank twice, no dirt in the fuel.

Could you possibly have any ideas - to me it sounds and feels as if the engine is now hunting a little on take off, allthough the rpm guage (electronic attached to left mag) shows fairly constant rpm around 2480) - I'm losing confidence in the motor and need some help here.

A couple of ideas regarding your problem.  It appears to be rpm specific, so that limits the possibilities a bit.  One comment, which may be an interpretation of Aussie terms:   You say that the engine started "hunting". Does this mean the engine started to miss, or the engine simply lost power and the rpm varied when reaching 2600 rpm.  I work for an Aussie company, so I understand most of the lingo, but sometimes get tripped up.

If the engine is lagging at 2600 rpm and then recovers as airspeed increases, it could be that your prop is stalling and then unstalls once the airspeed picks up.  This is a very common characteristic on engines/airframes configured with extreme cruise props.  The takeoff is somewhat sluggish, and the prop surges a bit as it unstalls and starts to take a bite of air.  My Cassutt configured with Hendrickson prop on an O200 did this very thing.  I tried various other props and finally found a Sterba prop which gave good results.  What is your rpm on the takeoff roll?  I'd wager that it is staying at about 2200-2300 rpm and then picks up once the Tailwind becomes airborne and accelerates.

If it is the carburetor, it could very well be a plugged jet which bogs down at high rpm.  The carburetor has several fuel/airbleed circuits for various engine intake velocities, so if one of the circuits plugs, then there will be a definite lag corresponding the rpm which drives that circuit.

If the magneto is breaking down at a specific rpm, then it could be that the points are bouncing.  Once again, this is very common to engines with wooden props and extension shafts.  The standard ignition harness set up is that tne mag fires the top plugs and one mag fires the bottom plugs.  The left mag fires the bottom plugs and usually has a higher and rougher mag drop than the right mag, which fires the top plugs.  Maybe the p-leads are reversed?

Changing the inlet manifold can cause problems.  If the runners are too short, or the depth of the airbox is too shallow, then the airflow may be insufficient or the mixture amongst the cylinders may not be equal.

A final idea is the carb air box:  If the heat flapper is loose or vibrating around, this will result in variances in rpm.  Typically, when the engine is pulling a lot of manifold pressure, it can suck the carb heat valve up and partial carb heat occurs.  Check to make sure that the flapper is secure and that the operating cable has enough friction to stay in a closed or open position.  Sometimes the cable creeps.

One of the problems with homebuilts is that nothing is standard, despite the fact that a certified engine is attached.  Lots and lots of variables with homebuilts.

Let me know how the situation works out.

Harry


Mogas vs. 100LL

What is your thought on running 87 octane auto gas Vs 100 octane avgas?I believe all auto gas in my area now is 10% Ethanol.I have STC for auto fuel and have metal needle and seat in carburetor.A65 requires minimum 73 octane at 6.3:1 compression.Does 100 octane burn completely at such low compression?Is burn rate slow enough to effect power stroke?Obviously, 10 % Ethanol reduces BTU content of auto fuel.Which fuel will provide more power?If we still had 80 octane avgas I wouldn't be asking these questions.
The primary differences between mogas vs 100 octane boils down to cost, availability, and some chemistry issues during operation.Once again, there is no hidden power to be found using 100 octane- the A-65 will still produce just 65 hp.

Generally speaking, mogas will run a bit sootier than 100 octane.Mogas does not "store" as well as avgas, so if the engine sits for extended periods of time, there tends to be more problems with the mogas gumming up carb parts.Avgas stays very stable over a longer period of time than mogas.An airplane parked for several months with 100 octane is less likely to have problems with the fuel system than one parked with mogas.

Chemically, a negative and a positive to 100 octane is the lead content. The lead serves to reduce the possibility of detonation (not required for an A-65) and to provide lubrication for valve stems.The lubrication feature is a plus for the A-65 as some engines can experience valve sticking problems when run on mogas.On the other hand, the lead content of 100 octane is higher than 80 octane, and it is common for the lead to foul spark plugs and sometimes cause valve seat erosion.

I tend to prefer 100 octane because my engine runs cleaner.However, I will run mogas from time to time.Over a years' time, I probably run 100 octane 70% of the time vs 30% for mogas.Is this a science?Nope, it is just how it works out for me based upon what fuel is available at the time I fill up..I never really have any lead fouling problems, perhaps because the mogas dilutes the 100 octane.Auto fuel, at least with the engine in my Champ, most definitely leaves a sooty, black deposit from the exhaust stacks.Plus it does not smell as sweet as 100 octane.I fly about 30 hrs/yr in the Champ, so I figure that it costs about $150 extra each year to run 100 octane.With current fuel prices, that means that I could get three extra tank loads over a year if I used mogas exclusively in the Champ.

Volumes and volumes have been written on mogas vs avgas, and there is simply no consensus (the discussion about Marvel Mystery oil is just as voluminous).It seems that engines each run a bit differently and results may vary, and neither fuel is exactly optimum.My opinion is that if there is no consensus, then either fuel has an equal chance of yielding positive and negative results.The choice really boils down to availability and cost.

Harry


Timing Adjust for Mower Power

Need your thoughts on bumping the timing on a A65-8 to 32L / 29R as used for an A75.

Engine is A65-8 on a J3 @ 400SMOH withSuperior Cylinders, new Unison Mags, overhauled McCauley metal climb prop.

I have run auto gas in this engine since overhaul with no problems.I mix 2 ounces of Marvel Mystery Oil / 5 Gallons gas to help top-end lubrication. Oil consumption is very low - 1 quart/10 hours.

I'd be a millionaire if I was paid a dollar for every question on getting more power from an A-65! :-)

To keep the engine legal as it is installed on a type certificated airplane, the timing must remain stock at 30/30 BTDC.I don't think that you will see any significant benefit from changing the timing to 32 degrees, anyway.I think that the primary function of the split timing is to even up the mag drop as opposed to any power benefit.The A-65 is what it is and not much you can do to up the output.Even the 75 hp conversion just adds a bit of oomph, not a kick in the pants.85 hp and up will give you the most noticeable performance improvement.

Harry


Running Rich

Harry like everyone I need advice. I have a Piper PA-17 newly rebuilt with an A65-8 with about 55 hrs one it. I put a McCauley 1B90 71-44 prop on it and cant get the RPM up to specs. The engine seems to be running rich, I have checked the float level and the main jet size and they seem OK . I am using auto fuel, the plugs are coal black the best I can get static is about 1950 with a tach which we have checked. I used to own one of these back in the 60s with an C65-8 and had lots of RPM but dont remember exactly what prop we ended up with was. I do know I got it with a 72-42 wood prop and changed it to a metal, but for the life of me I cant recall the specs on it.

I have had the very same rich running problem on my Champ.I have improved it, but not completely solved the problem.

First, my primer was leaking and a little bit of fuel was seeping into the induction.I tried a variety of the vintage Lunkenheimers, but finally installed a new production primer.The problem, improved, but was not solved.

Next, I began work on the carburetor airbox.The flapper valve was a bit loose and when the engine was pulling air, the valve would float a bit and apply a slight amount of carb heat.Carb heat tends to enrichen the mixture.When heated, the air molecules expand at a faster rate than the fuel molecules.The net result is more fuel to air molecules, which is a rich running condition.I replaced the airbox with a new one and problem solved.

Next, I tried a variety of spark plugs to find the right heat range.The best plug I found were the Unison Autolite Iridium plugs.These plugs are more expensive than a standard plug, but improved the problem.If your PA-17 cowling is stock, there is a clearance problem on the front plugs, so tunnels have to be built into the cowl to accommodate the taller plugs.

Finally, I took a look at the carb.It turns out it was jetted for a 75 hp engine, so I re-jetted for an A-65 and that continued to improve, although not completely solve, the problem.

I also tried various suppliers of auto fuel, but no luck.The plugs ran pretty clean, but there was always a slight sooty trail behind the stacks.

So, I tried 100 octane.The sooty deposits at the plugs and exhaust disappeared!I ran a couple of tanks of 100 octane with zero problem.

Then I switched back to auto fuel.The slight sooty deposit returned.I mixed a tank of half 100 octane and half auto.The sooty deposits decreased, but did not completely go away.I switched back to 100 octane and the sooty deposits completely disappeared.

So, while I did find several problems which contributed to the sooty deposits, I never completely solved the problem.A clear observation I made (and not limited to this one event) is that auto fuel runs sootier than 100 octane.I don't know why, but that is just what I have observed.

Moving in a big circle back to your question, I would disconnect the primer and cap the manifold pickup with a small rubber vacuum plug that you can get at an auto parts store and run the engine.If the deposits lessen, then it is a good chance that your primer is leaking.Leaking primers are the #1 problem.Otherwise, check the mag timing, plugs, etc.

Regarding the rpm, the first aspect to consider is the prop pitch.The Piper PA-17 Type Certificate Data Sheet, Page, 2, note 2specifies that a McCauley CM7248, not over 72", not under 71" is approved.Your prop meets the minimum diameter (71) and the pitch is 44.The standard pitch is 48, but there is a range of pitch which would include flattening the pitch to 44, which would provide more climb performance.At face value, your prop appears to be a climb prop, and, by design, the engine should actually turn more RPM than a standard or cruise pitch prop.The TCDS rpm range with this prop is 2150 to 2300, so you are under limits at 1950 rpm.

Low rpm can be caused by application of carb heat, which would also cause the rich running condition.So check to see if the airbox flapper valve is secure.Other than that, the severe rich running condition can certainly cause an rpm loss, so correcting this issue first will certainly lead to a solution for the rpm issue.

Harry


Compression on New Cylinders

I fly and maintain a wonderful L-4A.

After (stupid) a mishap with a ground propstrike I had my C85 (1730 hrs) overhauled and new Superior Cylinders installed.However after some 36 hours of flying I checked out why it had a hissing sound from the exhaust while turning the prop. The RPM seemed ok with almost 2400 (static) with my new wooden Sensenich W72GK-44. (However I think I would have been better off with at –46 for slightly better speed – agree???).

The compression check (cold engine) showed the following figures:

# 1: 74 PSI

# 2: 74

# 3: 72

# 4: 78

I found these figures unacceptable, and took the a/c to the overhaul facility, where we took cyl 1 & 3 off to inspect further.With the cylinders standing upside down filled with cleaning fluid absolutely NO fluid would pass the valves and come out to the ports!Inspecting the valves later there was a slight sign of leak on the valve flanges, and they were lapped with Carborondum.We took leak tests again on #1 & #3 without the rods installed (I was suspecting that the original rods might be too long for Superior cylinders?). Same figures!

I have broken this engine in with full rich mixture for the first 25 or so hours running @2500 initially, later reducing to 2400 during cruise. The engine uses practically no oil, and cylinder insides, rings and pistons look great.I have later leaned to not more than 2 units (50 degrees) below peak for cruise. Some say that that you should not lean below 5000’ – what do you recommend? 

I cannot understand why a new cylinder can leak through the exhaust (confirmed by sound and a hand against the muffler port) and have such low figures.

What is your experience with Superior, and what more can be done except changing the cylinders, claiming warranty???

Keep in mind that there is no specific compression number that a cylinder will have after 36 hours of operation or even 2000 hours of operation.The compression is allowed to fall within a range from high to low, and so long as the values fall into this range the cylinder is airworthy.

Continental has a specific procedure for a compression check.Using the Continental method, the upper number for compression is not as important as the low number and certain leakage at the valve and cylinder seals. Continental also uses a Master Orifice tool which calibrates the leakage gauge to the lowest allowable number for the atmospheric conditions at the moment that the compression is being checked.This tool is readily available from Aircraft Spruce, Aircraft Tool and Supply and many other companies.This Service Bulletin also has a detailed discussion on how to evaluate the condition of cylinders in terms of physical wear and oil consumption. Here is a link to the Continental Service Bulletin for the compression check:http://www.tcmlink.com/pdf2/SB03-3.pdf

From your description, it does not sound like there are any significant problems with your cylinders:the oil consumption is not a problem and the compression values fall within acceptable limits as established by the manufacturer, and no solvent leaked past the seats during a bench test.The slight hiss at the valve may be an issue, but the engine should be checked warm to have all of the dynamic seals properly fitted.Checking an engine cold is the hardest test, but the most practical test is when the engine is warmed to operational temperatures.Continental Service Bulletin SB03-03 specifies that the engine should be at operating temperatures when checking compression to yield the most accurate results.

Regarding your break-in, it sounds like you have operated the engine appropriately.Here is a link to the Continental Service Bulletin on engine operation after overhaul and cylinder replacement: http://www.tcmlink.com/pdf2/M89-7R1.pdf

Overall, other than you are disappointed with somewhat low overall compression numbers on a cold engine, you are not describing to me anything which would be alarming or unusual.I would re-check the engine using the criteria described in Continental SB03-03 and then make a judgment on the condition of your cylinders.

Harry


More On New-Cylinder Compression

I have a Cessna aerobat 1970 (0200a ).Sent my engine to a reputable shop to have it rebuilt.New cylinders continental , spit the case and had everythinggone over. No cost was spared on this job!

With that said after 25 hours with the break-in oil my compressions are low ( 70-72-74-70) Even had a reading in the 60's until moving the prop.I can hear air leaking past the exhaust valves as well as intake!Lots of case pressure.Standing next to the plane easy to hear air out the breather tube.This is the second set of cylinders originally installed millennium cylinders and had extreme case pressure.Oil leaks from every possible location.Swapped with continentals and all oil leaks went away.However as I mentioned above still have case pressure low compression and leaky valves and a breather tube that could be used for a leaf blower!If you can call me I can answer any questions you may have.This has been going on for well over a year and no one can get it figured out.Please help if you can. If you need any thing please call.Thanks in advance.

Boy, can't you guys send me easy questions?!?

When the engine was overhauled, were new pistons installed?If the piston ring grooves or piston ring lands are out of spec, it is possible to get blow-by.The grooves need to have a minimum diameter as the piston "grows" when heated and pushes the rings outwards towards the barrel wall.

Nest, were the rings replaced when the cylinders were swapped from Millenniums to TCM?Could be you have a bad set of rings, and it just appears that the cylinders are bad.However, I'm assuming that the new TCM cylinders can with rings, piston and pin as this is how TCM sells the package.However, were the TCM cylinders new or rebuilt?This makes a difference.

Another long shot with the rings is if the wrong rings were installed. Cylinders with chrome surface walls require cast iron rings, and plain steel cylinder walls require chrome rings.If cast iron rings are used in a steel cylinder, they will rapidly wear, resulting in high case pressure.Once again, both the new Millennium and TCM cylinders have steel barrels and I assume that new rings were installed at each swap.Rebuilt TCM cylinders may have chromed or steel barrels.

Was the compression check done with the engine warmed to operating temperatures?This will yield the most accurate results.A cold engine will yield the least accurate results as the parts fit is loose and tightens as the engine is at operating temp.

The hours required to break in an engine are not a fixed science.Usually a four cylinder Continental can be considered broken in after 50 hours. Sometimes the process takes longer, sometimes shorter- it is not a science. When breaking in, the engine should be run at 75% power or better- don't baby it as the rings need friction and heat to break in.Too little power and the cylinder barrel will glaze and not hold compression.An O-200 should be run at 2500 rpm or better.I run at full throttle for the first 10 hours, reducing the rpm to 2600 and 2500 and then increasing to 2700 rpm every 20 minutes during each sustained hour of flight.Don't fly less than an hour when breaking in the engine and don't do extended ground runs. Breaking an engine in on the ground does not work and is certain to result in glazed cylinders.

I'm kind of thinking that you may need to fly some more hours to get to the 50 hour mark and then make an assessment.I have to tell you, nothing is impossible, but I think that it is pretty tough to get two batches of bad cylinders from two different companies.The most likely condition in my thinking is that the cylinder walls are glazed and the rings can't seal and make compression.

Here is a link to the TCM Service Bulletin on testing engine compression: http://www.tcmlink.com/pdf2/SB03-3.pdf

Harry

Follow-Up….

Yes new pistons installed.

Engine was flown just before compression check. operating temperature was achieved.

Break-in flights were performed as per Cessna pilots association (CPA) recommended procedures. Engine was broke in correctly and was not babied. never flown less than an hourand short ground runs.I Can assure you that improper break-in was not the issue.Still not sure why valves are leaking and compressions are so low.Why so much case pressure?I've never had an engine leak so much from valves when dealing with these engines.Some thing else seems to be going on.Can the push rod lengths have any effect on valves closing?Can this be adding to the case pressure and not allowing the valves to fully seat?I will continue to fly the planeand hope for the best.The cylinders came with kits and hopefully they were installed correctly?Something is definitely going on.Can't put my finger on it. Thanks again for you insight and taking the time to offer up some tips and suggestions.Much appreciated!!!

This is one of those situations which I am probably not going to be able to answer.I would really need to physically inspect the engine to make any reasonable comments.Working in the blind via the internet, I can only guess, and that isn't going to help.Your on-site mechanic will be knowledgeable about this engine and will be able to offer useful guidance. Maybe a second opinion from another maintenance shop may help.

Regarding the pushrods, yes, they can affect valve opening and closing. There is a stack up of tolerances based upon valve stem length, the depth that the valve head recesses into the seat, the thickness of the rocker arm face, etc.However, the valve lash is pretty wide, so it is rare for pushrod length to be an issue.

Sorry I can't give you a solid answer- you should not see the same problem over two different sets of cylinders.

Harry


Radio Noise from Mag

There is a great amount of ignition nose in the radio from the right mag (mags are Bendix). The right mag fires the top plugs, and they are encased in shielding cans which are probably supposed to contain any radio noise. I am using an ICOM handheld hooked to an external antenna, a stainless bent whip. Would the noise source most likely be in the mag itself, ignition harness, shielding cans, or the connection, terminals instead of a BNC connector, to the whip antenna? Thanks again for your assistance.

Most of the time, ignition noise which affects the aviation radio spectrum, 108-138 mhz, is radiated from the ignition harness or spark plugs.Those little shielding cans were adequate when there were only 180 channels spread out across the spectrum, but now there are 760.The tighter frequency range is more susceptible to picking up the RFI generated by the spark plug wires. The magneto can produce some noisy frequencies, but these tend to fall into the ADF range.

If you can use shielded spark plugs and harness, that would be the best method to sort out the noise issue.You don't specify, but it sounds like there may be shielded plugs on the bottom cylinders.If the radio is noise free when operating on the bottom cylinders only, then it is certainly RFI generated by the top, unshielded plugs.I also assume that the Mong has a plug-to-cowling clearance issue, hence the shielding cans on the plugs.The shielded plugs and harness are taller than the unshielded set up and will probably require that the cowling be fitted with some clearance bumps to make room for the spark plug connection.

The low dollar fix is to just run on the quiet mag when using the radio.

Harry

Follow-Up

Harry, latest update. I gave in and replaced the top plugs with four new Champion REM40Es. Also replaced the harness wires for the right mag. Had to cut clearance holes for the plugs in the top of the cowl and put fairings over them. Used fairings meant for the Mooney Cadet. Actually looks pretty neat. The most important thing, it fixed the radio noise. Got all this done just in time too. Most of us at SummitAirport in Delaware where my Mong is based are losing our hangar space. I was able to get into a hangar with a friend at the big airport in Wilmington. It's a fairly busy controlled field so a good clear radio is essential. 


Stuck Float

Question about an older type carb installed on a C-90. I believe it is a Stromberg, for sure it is not a MA3SPA. It does have a mixture control, but it is wired in the full rich position. It looks like the carb that was on my C-85 powered Ercoupe of many years ago. The C-90 with this carb is installed on a Mong biplane that I just acquired. I was about to make my first flight in this airplane yesterday. I started the engine it ran for a few seconds and quit. I discovered fuel vigorously leaking out of the bottom of the carb heat box. Couldn't find any leaks anywhere.Finally tried tapping on the carb float chamber and the leak stopped. My question is; is this likely to reoccur even if I start it and it runs normally? And the real biggie, is it safe if runs normally on the ground? Really need some advice from someone that knows these older engine and accessories. Thanks.

I have had two Mongs in the past, and my friend Ed Fisher is the Mong expert.Go to http://www.raceairdesigns.com/index.htm for more info.

It sounds like the float stuck, which happens from time to time.The carb mixture is usually wired open as it really does not provide much leaning effect.

As with all homebuilts, the question usually is:What is the condition of the engine?Has this airplane been flying regularly or has it been parked? Are there any clear or detailed records of when the engine was last overhauled or serviced?Usually, the logs on homebuilts are not very detailed.I wouldn't be surprised if there was a general entry that the engine was "overhauled" with not much detail.

Regarding the safety of flight question, only the pilot or mechanic can make that determination.It is impossible to make any assumption via the internet without physically inspecting the engine.In this world of litigation, it is insane to make any assumption of airworthiness via e-mail. My advice is to not fly until you have sorted out the problem or understand why the float stuck.

However, if you provide some more info, I can make some general comments on how to troubleshoot the problem.

·When was the carb last overhauled/serviced

·How many years/hours in service

·Auto fuel or AvGas

·Has this aircraft engine been active or in storage

·Has a condition inspection been completed by a rated individual. Only the original builder or A&P can perform a condition inspection.

Drop me a line back and I'll see what I can offer for comments.

Harry

Follow-Up

Harry, thanks for the advice. The problem seems to be resolved. The engine has run flawlessly ever since that incident. Have been flying the Mong regularly, but staying very close to the field. I contacted Ed Fisher. He is a great source of Mong information. He even knew something about my Mong and the Stits playboy I had.


Low Max RPM

I have a Playboy, sitting 5-6 years, getting it ready to fly again. The C-75 (previously converted to 85) during run-up gave a 2350 RPM full power static but would not run below 1000 RPM. After a trip to the carb shop it now idles but only 2150 full power static. Full movement throttle arm OK, gravity flow fuel check good, all other parameters same as before the shop. The shop enlarged the main jet trying initially to cure the idle problem (finally found obstucted idle tube). Could a too rich condition cost the 200 RPM? Is 2150 full power static enough to fly? Is there an acceptable range of static RPM (given a range of propeller pitch/ length)? I don't have my propeller specifics with me at this time.

No way to be certain, but I suspect a prop pitch issue.Have you flown this plane before?If so, I am assuming that it developed more than 2150 rpm. What is the altitude of the field at which you are based?This makes a difference, too.

If the engine was so rich it would reduce engine rpm, then the plugs should show a lot of sooty deposits, or so I would think.The carb is probably an NA-S series with no mixture control, so you are somewhat limited in what you can do to pull the mixture to see if the rpm increases.If you had a MA series carb, I would just suggest leaning the mixture to see if the rpm increases.

Here is something to try on the ground, though, which may kind of explore the mixture issue.The primer attaches to a port in the spider just after the carb.Connect a piece of rubber tubing to the fitting, long enough to run to the cockpit, and plug the end with a dowel.Start the engine, set up the engine to a stable running rpm, and pull the plug.The engine should pull enough air in through the tube to lean the mixture, maybe even enough to kill the engine.Modulate the airflow with your thumb to see if the engine rpm changes.If it improves with more air, then the mixture is clearly too rich.

My disclaimer though:I can't guarantee that the tube trick will work, but it is a low buck method to aggravate some sort of change in the mixture.

One last thought:Run the engine minus the air filter.Maybe it is simply plugged, causing the engine to choke down.

Regarding your question if 2150 is enough rpm to fly:this is a good question, and only you can answer that.One of the downsides to homebuilt is that they are experimental and there is an element of risk to be assumed by the builder/owner.The prop will have a strong effect on engine rpm, and no telling if the prop you have is set to any standard.See if you can get more info on the prop and we can go from there.

Harry

Follow-Up

An update. First, the Playboy flies well. After looking everything over, I can find nothing wrong except my faulty recollection of pre- carb shop rpm (2350???). The prop (70X54) indicates cruise. I did check most of the items you suggested, including the electronic tach. All seems well excepting the possible need for more of a compromise propeller (less pitch, more length). Thank you for responding-the problem was pilot error.

No way to be certain, but I suspect a prop pitch issue.Have you flown this plane before?If so, I am assuming that it developed more than 2150 rpm. What is the altitude of the field at which you are based?This makes a difference, too.

If the engine was so rich it would reduce engine rpm, then the plugs should show a lot of sooty deposits, or so I would think.The carb is probably an NA-S series with no mixture control, so you are somewhat limited in what you can do to pull the mixture to see if the rpm increases.If you had a MA series carb, I would just suggest leaning the mixture to see if the rpm increases.

Here is something to try on the ground, though, which may kind of explore the mixture issue.The primer attaches to a port in the spider just after the carb.Connect a piece of rubber tubing to the fitting, long enough to run to the cockpit, and plug the end with a dowel.Start the engine, set up the engine to a stable running rpm, and pull the plug.The engine should pull enough air in through the tube to lean the mixture, maybe even enough to kill the engine.Modulate the airflow with your thumb to see if the engine rpm changes.If it improves with more air, then the mixture is clearly too rich.

My disclaimer though:I can't guarantee that the tube trick will work, but it is a low buck method to aggravate some sort of change in the mixture.

One last thought:Run the engine minus the air filter.Maybe it is simply plugged, causing the engine to choke down.

Regarding your question if 2150 is enough rpm to fly:this is a good question, and only you can answer that.One of the downsides to homebuilt is that they are experimental and there is an element of risk to be assumed by the builder/owner.The prop will have a strong effect on engine rpm, and no telling if the prop you have is set to any standard.See if you can get more info on the prop and we can go from there.

Harry


Fuel Drip from Carb

I recently purchased a PA-11 with a Continental 85-12F.The aircraft has been in wings off storage for over 11 years.So far everything about the engine is looking good, including an excellent cold compression check.We have not yet run the engine.

My question is this.The carburetor is wired to full rich and there is no mixture control installed. After putting fuel into the airplane, the carburetor is leaking approximately one drop every six seconds or so whenever the fuel valve is on and the engine is not running.Is this normal for this engine?It would require turning off the fuel valve after every shutdown to stop the fuel drip.I don't mind the requiremnt of doing this, but I just want to know if it is normal for the carb to drip fuel in this way.

The condition that you describe is relatively common.The slight fuel drip will not be an issue when the engine is running.

The situation is that fuel is leaking past the float needle valve.This valve should shut off the flow of fuel when the float rises to a certain level and pushes the needle valve down onto the valve seat.If the valve does not seat, the float bowl overfills slightly , dripping fuel through the carb.This leaking affects a fairly good percentage of the Stromberg carbs. Some of the needle valves have a rubber or composite tip, some are metal to metal contact.Auto fuel has been known to swell the rubber tipped valves which causes the sealing face to distort.The metal to metal valves and seat can be carefully lapped to get a good seat.There is considerable controversy over which valve works the best, but current opinion tends to favor the metal to metal combo if auto fuel is used.Incidentally, I have noted that the complaints of this situation are much higher with auto fuel than 100 octane.

The cheapest, easiest fix is to turn off the fuel selector valve when the aircraft is parked.A more elaborate fix is to have an experienced shop work on the carb and replace the valve.If you go this route, I would recommend Aircraft Systems in Rockford, IL, 815-399-0225, http://www.acs-rfd.com/or RLB Accessory Service, Addison, IL 630-543-9213. These are my two favorite shops for accessory work in my local area, although there are many other fine shops throughout the US.

You might want to just fly the plane for a bit and see if the problem improves or gets worse.My Champ carb leaked like crazy after sitting for decades and then actually improved over several months of continued operation.

Harry


Dropping Oil Pressure

I have a Continental A-75-8, S/N 79000 engine on a WagAero Cubby. It has about 600 hours on it since its last major overhaul.

It has been flown about 50 hours since its purchase last year and just came through its AI Condition Inspection with flying colors.

After two months downtime during a recent spell of bad weather along the TexasGulfCoast, I began flying it again.While out on the first return to flight, I noticed the oil pressure was slowly dropping down between 140 and 160 degree F from 35 to 20 psi at cruise.Soon, the pressure would start at above 35 psi and drop to 15 psi before I shut it down.

I have gone through the following steps: 

1.Replaced the oil pressure gauge with a new aircraft gauge - No improvement 

2.Changed oil (Aeroshell 100 50W) - No improvement

3.Shimmed, then removed the pressure relief spring and visually inspected the sealing surface- No improvement

4.Installed new oil pump gears, cover plate, and all newaccessory case gaskets and seals.Oil pump housing and gear set clearances are all within tolerances(gear lash, and gear to housing clearance were measured with a feeler gauge, and end play was measuredwith a dial indicator).There does not appear to have ever been any damage to the oil pump housing - No improvement

It appears the next step is a major overhaul.That is a shame because the engine runs great.Do I have any other options before taking this final step?

One cause of degrading oil pressure is worn main bearings.Probably, when the engine was overhauled, the crankshaft journals were not ground to make them concentric.When the crank is ground, oversize bearings are installed to bring the bearing to crank tolerance to new limits.However, cranks for the 65/75 Continental are relatively hard to find, so removing metal is usually a last resort to bring a crank into limits.

Another very real possibility is that the bores in the case that the lifter bodies pass through are worn.This is a relatively frequent problem and requires that the case be sent out for overhaul.I am leaning towards this as a problem, but hard to tell until the engine case tolerances are checked.

The oil pressure can also be an issue with the oil pump.The oil pump cover plate can sometimes be touchy and won't seal right.I have fiddled with the torque to get the plate to seal correctly.

Your engine is definitely giving you indications that something is not right, and is in a relatively slow mode of degradation.Loss of oil pressure is a fairly big system problem, and the only way to investigate is to tear the engine down, assuming that the oil pump has been eliminated as a cause.You may not need a complete overhaul, perhaps just the crank ground or case overhauled.The A series engine is uncomplicated and can be knocked down and reassembled over the course of a weekend or two.

Kind of a tough call, as once the engine is open, the desire to overhaul the entire engine gets pretty strong.However, there is nothing wrong with repairing to serviced limits, either.My Champ engine has about 10 years on this type of repair and it is chugging along quite happily.As long as all of the limits within the engine fall within either a service or new spec, you should be able to realize several years of good operation.

I'm assuming that you are operating near Houston, given the NASA address and reference to Texas.Clover Field has a lot of homebuilt and antique airplane resources, so you might be able to find some help or advice on a Saturday when the hangar doors are open.

Harry


More Oil Pressure Dropping

Harry,I just finished restoring a '46 7AC champ,with the project was a 0SMOH A-65-8 engine that was overhauled in Jun '88,the engine was packed in a box with dessicant bags around it, I put new slick mags,leads and REM37BY plugs in it, it started fine and I ground ran it for about 15-20 minutes, then changed oil, no leaks, then taxied it for about 30-45 minutes, changed oil again, ran cool, and no leaks, then flew it for an hour. 

It does not have the oil pressure I would like to see, start-up 42 lbs then drops to around 18-20 lbs, and idles at 5 lbs, I believe 10 is the min.My major problem is at high RPM's it hasa miss, it happens around 2000 RPM's, I've got a W72CK44 Sensenich cruise prop on it, and had the Stromberg carb NAS3B-1 overhauled by Martin Induction in Enid, OK. I have taken off the mags and put them on a tester, and they check ok also the plugs and leads check ok, I've checked with some of the local engine people andEl Reno Aviation in OK.and they say run it for 25-50 hours and see what it does then.it runs cool and sounds good, mag checks in the green,it may have a couple of dragging valves that MMO and running it might clear up.What are your thoughts on this?

Generally speaking, oil pressure is sum of the tolerances of the oil pump and bearing to journal clearances.If the tolerances are tight, then the expected result should be good oil pressure.When the engine was overhauled, if there is no record of the tolerances, then it is reasonable to assume that the tolerances were not checked and new bearings and gaskets were probably tossed in and an entry stating "engine overhauled" written into the logbook.Unless there is an entry that the crank was ground, or a set of journal dimensions, then you really don't know what you have.

More than likely, the oil pump cavity is worn.The oil pump cavity can become egg shaped, or become grooved from bits of metal debris circulating through the engine.The holes where the oil pump gear shafts pass through are important, also.If the hole is too big, then the pump won't maintain pressure.Finally, the oil pump cover needs to fit flat on the oil pump housing.Sometimes, tightening and re-tightening the securing hardware can make a difference.

Be prepared to have the accessory case on and off a few times during the troubleshooting process.While it is off, check the pump cavity thoroughly and confirm that the gears have a proper backlash.If the tolerances are worn, just bite the bullet and ship the case off to Drake Air, www.drakeair.com <http://www.drakeair.com/> , and have the oil pump fixed once and for all.

By the way, you will be advised to place washers under the oil pressure relief spring to increase oil pressure.This does not work.It is kind of like saying that a clogged artery makes a weak heart exercise more and it is a good thing.The oil pump needs to move the spring without any washers, so fix the pump.

The rough running could easily be a sticking hydraulic unit or a sticky valve.It probably won't hurt to run the engine a bit and see if it loosens up.If the condition does not improve, then the valves will need to be pushed out and the guides reamed.MMO probably doesn't hurt, but there is no scientific proof that it actually helps.But, like I say, it doesn't hurt, so why not give it a try.

Overall, run it a bit and see how it goes.The low oil pressure may be a bigger problem than the rough running.

Harry


A65 EGT Range

I fly behind a Cont. A65-8F and I have been jogging aroundtheinternet looking for normal and maximum EGT temps but thus far I havenot found any useful information. I have an EGT guage with a set ( byprevious owner ) red line, but have no way of knowing if it isrealistic and cannot ask the previous owner about this as he has passed several years ago.

Can you shed any light on the acceptable egt range?

Neither the Continental manuals nor the Type Certificate Data Sheets specify a maximum, or any, EGT limit or range.A CHT maximum of 550F is specified by the TCDS, though.

EGT is usually a relative number.When the engine is leaned, a peak temperature is reached when the fuel/air mixture is balanced to peak burning efficiency.Typically, the engine loses power just as the peak balance point is crossed into a lean of peak point.Some engines will suffer accelerated wear of the valves when run at peak or lean of peak due to the higher temperatures at and beyond the balanced peak point.

EGT indication is also subjective to the probe placement.If the probe is too far downstream of the exhaust gas, then the indicated temp will be low. Also, ambient temperature and humidity will affect the peak temperature from day to day.Also, due to imbalances in the induction system, peak temps will vary from cylinder to cylinder.

An observation of the relative temperatures on a Lycoming engine which I operate with an absolute EGT gauge indicates about 1450F-1380F for a cruise EGT.The Alcor gauge in another airplane I operate does not even provide any actual temperature readings, but rather a graduated scale of markings. The engine is leaned to a peak temperature, and then enrichenedto provide a minimum 25 degree rich of peak operating temperature.I don't have any four cylinder Continentals fitted with EGT gauges at the moment, but I think that these numbers may be similar amongst carbureted Lycoming and Continental engines.

Here is a link to a manual for an EGT gauge:

http://www.insightavionics.com/pdf%20files/GEM%20GUIDE.pdf

There is a theory of operation section which provides much more detail as to how to operate an EGT gauge, but the basic concept will remain pretty simple.EGT is a relative temperature as opposed to an absolute temperature.

Harry


Which Side for the Impulse Mag?

I have decided to get just one Slick impulse mag to replace just one of the two non-impulse mags I have.I was wondering if there is any rationale to which side it should go on.Mattituck indicates, probably more historically than anything else, that when replacing only one non-impulse mag with an impulse mag, the left side is the correct side to do.In reality it seems to me there is probably no difference from one side to the other.If we are merely talking tradition of some kind, then left it is.Certainly if you say otherwise, I will follow your lead.Left side, right side, basic logic? Thank you very much for your help.

Mattituck is correct in that the traditional placement of a single impulse magneto is the left side, but it probably makes little difference between right and left.The A-65 ignition harness is set up so that the left magneto fires the bottom plugs and right one fires all of the top plugs.I would tend to have the mag connected to the bottom plugs be the one with the impulse as the priming fuel would tend to settle to the bottom of the cylinder and would be more likely to be fired off.So, perhaps a bit of science to the left position for the impulse coupled magneto.

The Slick K4335 mag/gear combo, M1960 ignition harness and 4 UREM37BY plugs is the best combination of parts to install a single impulse magneto.You may want to check on the price of a complete K4334-37BY kit to see if this makes sense, also.The price of a complete set up may not be that much more that a half kit.

Harry


Storage and Mag Selection

I have a zero time Continental 65 with rebuilt Bendix non-impulse mags.I am putting it into a Fisher Flying Products Dakota Hawk within the next year(have to finish building the Hawk)The engine is sitting in my heated(65 degrees on the thermostat), and dehumidified basement, with oil in the system, and dessicant plugs in place.I have a couple of questions for you:

1.It is probably going to be one year before the whole thing is hauled out of my basement and the next phase begins, fuel flow tests, weight and balance checks, final inspections, engine run-ups, and then flight testing. Do I need to do anything further to prevent "corrosion" or whatever in the engine that is sitting idle?I do periodically squirt a few drops of oil into each cylinder and turn the crank over a fraction of a turn. 

2.Everyone is telling me that I have to get impulse coupled mags, either one or two.Apparently the newer versions of the Slick mag product line are much better than the old ones so probably I would get a Slick product if I do this.What are your thoughts on whether I should get just one mag rather than two, and if you agree with just one, which side does it go on if it matters. 

3.If I get just one Slick, I probably would keep the swapped out Bendix as a "spare".If I go to two Slicks, I probably would try to sell the Bendix mags.Is there any market for these, and if so, what would you guess they are worth? 

Certainly appreciate your time.Take care.

Here is a link to the Continental Service Bulletin which details engine preservation for storage:http://www.tcmlink.com/pdf2/SIL99-1.pdf

Regarding the mags, here is the summary:

Any magneto works, so long as it is in good repair and adjusted properly. Non-impulse magnetos require that the prop be swung vigorously to make sure that a hot spark is produced and the engine rotates fast enough to get the crankshaft to continue to rotate in a forward direction.If the prop is not swung fast enough, then the engine can "kickback" or fire and reverse direction due to the lack of forward acceleration to keep the crank moving forward to overcome the ignition cycle.

Impulse coupling are spring loaded devices which latch and hold the magneto rotor shaft to delay magneto firing to an optimum starting point while the crankshaft is turning.When the impulse coupling unlatches, the magneto rotor shaft is accelerated and produces a hot spark, but delayed to a point to prevent kickback during the starting cycle.

The primary reason for using non-impulse magnetos is cost.From the practical operational standpoint, impulse coupled magnetos are the only way to go.

It is possible to install one impulse magneto, but the relative cost of installing a Slick K4334-40 ignition kit with two impulse magnetos is not much more that scrounging up all of the parts separately.The K4334 includes everything:New mags (not rebuilt), new harness, new magneto drive gears, new ignition harness, new spark plugs, and gaskets.This ignition kit completely eliminates any concern about starting, serviceability and reliability.Two impulse magnetos mean that both magnetos are producing a starting spark, not just one.Also, there is a slight operational issue in that the non-impulse mag must be turned off during start to prevent kickback.Remember, the first spark wins, so the non-impulse mag can still cause the engine to kickback during start when paired with an non-impulse magneto.

Slick offers a core refund and a rebate for purchasing a kit.Check with suppliers like Aircraft Spruce for the latest deals.

Harry


Building Up Pump Area for Low Pressure Problem

Hi Harry, I have a C85 with the dreaded oil pressure loss after warm up, and Iwill take the simple steps you have mentioned first, but should thesenot solve the problem then I have an idea or two that I would like torun by you for Experimental engines.My engine has 2580 TTIS, with 580SMOH and runs chrome cylinders with good compressions. I notice that you state the A65 has a magnesium alloy accessory case,do the C85, 90 and O200 also have magnesium cases? I am thinking aboutwelding mine to build up the wear area in the oil pump cavity and thenmachine it back to stock dimensions. I have a tame aluminum welder, buthe will not touch magnesium! What about milling any wear marks out of the stock oil pump cavity andfitting oversize gears; like .010" oversize in diameter. Are new oilpump gears available and can they be bought oversize? Maybe bore outthe shaft bearing and fit an oversize shaft, or bushing while I am inthere. I have an engineering friend who makes gears for industry and he saysthey are time consuming to make but not difficult, and 010" oversizewould be easy to make. He has hi tech EDM machinery to cut the gears,and has made camshaft gears for racing motorcycles and industrialmachines etc, with fine tolerances. You mentioned you had a friend in Canada, I think, with an insert forthe oil pump, anything come of that idea? I enjoy your column and have learned a lot from your writings. I am newto Continentals, but have 25 years of VW and Franklin background inairplanes. 

First off, in the world of homebuilts and experimental aircraft, anything is possible.I tend to stick to providing answers regarding stock, certified repairs, so I may not be able to offer much to answer your question.

I am not aware of any oversize gears, and I am not sure if that would be possible.The problem that I see is that the center "pinch" point between the two gear shafts would not really lend itself well to an oversize gear.

Welding of the magnesium case is a very specialized repair and best left to shops with a lot of experience.Experimenting with welding magnesium is a one-way trip, and once the weld goes bad, the part is going to be in worse shape from where you began.

Typically, the full repair for the oil pump cavity involves returning the bore back to stock diameter and re-bushing the shaft holes with bronze inserts.The most experienced company for this repair is Drake Air, TulsaOklahoma, www.drakeair.com.The cost of the repair runs about US$750 or so. A big benefit of Drake is that the part will be fixed and ready to install with essentially no hassles once it is repaired.

Drew Fidoe from the Fly Baby group has conjured up an experimental field fix, but he has only just begun to operated his engine since the repair, so he really doesn't have any feel for if the repair will hold up for the long run.Drew's e-mail is dogsbody@telus.net and I am sure that he would be happy to share the details of his repair.

My opinion is as follows:If you want to simply get the case fixed and re-install with no continuing hassles, send it to Drake.I am guessing that you will have about AU$1200 into it from start to finish.If you are prepared to experiment and tolerate on and off success with the potential of having to remove and re-install the accessory case a couple of times to get it right, then go the experimental route.

One final thought:There is a company in Australia which may have the capability to work on magnesium bits.Contact Rudy Spiesel at Rudy's Aero Engines Ltd, Sale, 351 49 2300.Rudy is a consummate tinkerer and helpful with experimental engine work.He's a mate of mine from many years, so feel free to drop my name.

Harry


Bearing Wear and Oil Pressure

Hi Harry,I had contacted you a couple of weeks ago about an A-65 with anapparent oil pressure problem........turns out that a 50 hours since major engine is pretty much gone in the lower end.The crank was turned020 on the rods and 010 on the mains by Aircraft Specialties.The casewas reworked by CSI in Sand SpringsOK.Aircraft Specialties also donethe lifters and rods and we installed a new camshaft.We were very careful about cleanliness and pre-lubing when weassembled the engine and it held excellent oil pressure for about 30hours before starting to slide. The screen never showed metal.We tore the engine completely down and the crank and main bearingsshow a lot of wear and grooving on the main journals and the wear isnon-symmetrical, heavier on one side of the journal.Everything is backat the shops now.I had several mechanics look it over and they allagreed that something was not right in the crankshaft/case journalarea.We put the crankshaft in a lathe on centers and checked runout onthe center journal and it came in at .0022....within the .035 tolerance.Any thoughts?Thanks.

My initial thought is that the crank may have been ground only .010 instead of .020.If the .010 crank journal was fitted to .020 bearings, the fit would be too tight and wear will occur.Conversely, if the .020 was fitted with .010 bearings, the fit would be too sloppy and certainly would result in high wear and low oil pressure.Maybe something insane like one .010 bearing shell half and one .020 was installed.I've never heard of this happening, but you never know.

If you check the back of the bearing shells, there should be something like M010 or M020 etched into the surface to denote .010 and .020 undersize. Never trust what is printed on the box- always check the marking on the bearing.It is also common to fit the bearings to the case, torque the case together and then measure the ID of the bearing bore before fitting the crank.

Most of the really good engine shops measure and inspect all parts, even newly finished parts and knock down cylinder assemblies to make sure that the factory assembled them to correct tolerances.Most quality systems won't even assemble parts together until subcomponent tolerances are confirmed.

If the case bore was misaligned, then this would cause a problem, also. During case repair it is common to re-weld and machine the bearing saddles to return them to a standard diameter and then align-bore the centers to make them true to center.Obviously, if alignment was off, then there would be a sideload applied to the bearings and crankshaft.The bores may be ok dimensionally, but the alignment of the three bores along a longitudinal line needs to be checked.

Another possibility is that the bearings shifted in the saddle.However, this would have probably resulted in lack of lubrication and bluing of the crankshaft due to heat.

Let me know how it all turns out.

Harry


Oil Pressure Drop at Operating Temperature

I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.

About half the questions I answer regard low oil pressure on these little Continentals.

If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.

A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.

I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.

If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.

The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.

So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.

You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, TulsaOK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.

If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.

Harry


A65 With Starter and Other Mods

I have an A-65 that has been modified ay an AME with 85 Jugs and Pistons- all internals have been balanced by an aircraft shop, 85 intake spider and carb jetting, 0200 oil tank and starter and alternator, two slick mags .The engine has about 55 hours on it since the work was done.It seems to run strong and smooth, 2400 static rpm.What are your thoughts on the longevity of the engine with these mods.I would like to cruise at 2400 rpm which produces about 140 mph in my bird.

Regarding the longevity of the engine, who knows?Even in a stock state, the TBO is largely an estimated figure which can be increased or reduced due to a wide range of operating conditions.In the perfect world, the A-65 should provide 1200-1400 hours of use when operated on a regular basis. Lack of use is usually the big killer of engines over the long run.Engines which are run routinely day in and day out last longer than engines run 25 hours each year.

Regarding the revs, Steve Wittman once said something along this line:Each engine is designed to provide so many revolutions throughout its lifetime. Give or take a couple of hundred rpm, the revs are just used up at a faster or slower rate.As a qualifier, there is a crossover where high rpm also loads the crankshaft and reciprocating section with torsional or bending loads which the OEM may have never had a reason to investigate.So while somewhat higher revs probably don't make much difference, exceptionally high revs probably cross over into uncharted territory.

The weak link in the A-65 at high rpm is the connecting rod.The holes for the connecting rod bolts in the rod tend to wear oval over time which allows the saddle of the connecting rod to wiggle around and eventually the bearing shell can work loose and spin.This is loosely referred to as "throwing a rod" when the assembly lets loose.Valve float can be a problem with the A-65 valve springs, but the C-85 should not be a problem as these springs run at 2700 rpm with no problem.Other than that, 2400 rpm is not pushing the A-65 too hard, at least compared to the 3400-3600 rpm which the Formula 1 racers turn.

But, since your installation is experimental and unproven, who knows? You'll have to fly for a bit and keep an eye on the engine condition.As experimenters, we simply have to assume the risk of changes we make to stock components with a balance of sound judgment and accepting that something might go wrong due to unexpected consequences of the change.One reason that I limit the bulk of my conversations to stock configurations is that I can be reasonably assured of the long term success of the stock configuration.In other words, there is a certain bulk of evidence which supports stock configurations.

The starter set up is interesting- lots of homebuilders ask if starters can be mounted, so thanks for the photos.

Harry

Update [RJW].I received another picture of an A65 starter conversion from Mr. Paul Ralph.“I got fed up with hand propping and also got busitus in my shoulder so after giving up on trying to get the missus to start it, I pinched the starter and flex plate off her chevy sprint and put it to good use.It seems to work well and spins the motor with extraodinary vigour as well as starting the thing.The motor mount is bolted together using steel tube and bushings to put the loads in friction rather than shear (which fatique fails).”

One thing I hope is clear is that this is not a simple, bolt-on process.It takes some machining skills.


Serial Numbers…Locations and Other Issues

I bought a Taylorcraft with a c-85 12 in athat has no data plate- The engine was installed in the early 70 and has a log book.Is the serial number stamped anywhere on the crankcase or is there anyway of verifying the serial number to match it with the logs?

The serial number of the engine is usually not stamped on the case, but I may be wrong.

Replacement data plates are available from Fresno Airparts.Find copy of Trade-A-Plane and check out the first couple of pages and you will find an ad fro Fresno.Of course, your mechanic will need to do some reasonable work to assure that the logs match the engine installed on your plane.

One reason that the data plate may be missing is that the C-85-12 may not be approved for a BC12 unless the correct paperwork has been accomplished to convert your T-Craft to F-19 status.The F-19 change requires different struts, motor mount, prop, etc.If your T-craft is still listed as a BC12 series with no note for conversion the to F19 status, then it is not a legal installation.I've seen this several times in the past.The C-85 will physically mount the same as an A-65.The engine is installed and the data plate removed to disguise the illegal installation.

On a positive note, if the installation is legal, then, reasonably speaking, a new plate can be purchased from Fresno and re-installed.

Harry

Another Serial Number Question:

Could you tell me the valid serial numbers for the A65?I purchased an experimental with this engine and the engine log serial numbers don't match the engine data plate.The log s/n is:5860178 and the data plate s/n is: 351591.

The engine was pickled for 30 years pretty well.I had to pull the cylinders and clean the congealed oil from the lifters.Replaced the rod bolts, lightly honed the cylinders and replaced the rings, lapped the valves.Overhauled the Eismann mags.

It runs perfectly now with great compression (all over 76).

Could you suggest how I can start a new log book for this engine since I effectively have none?

I am not aware of any serial number listing archive for Continental engines. You will need to call the product support line at Teledyne Continental Motors to get some guidance- 800-718-3411. Be patient it may take some time to get in contact with the right person.

Otherwise, a new logbook can be generated to log maintenance and condition from this point on.The initial entry would read something like this: "Previous logbooks lost, hours unknown."followed by a summary of the work you have detailed below.Any attempt to make an estimate of previous hours on the engine will carry no weight as you cannot verify the hours and when the engine was overhauled.In essence, you will record the current condition of the engine with no reference to the past, and continue to operate the engine on a conditional basis until inspections or operational experience indicate that an overhaul is required.Once the engine is overhauled, the clock can be re-set and a more traditional set of logs can be generated using the date of the overhaul as a documented starting point.

However, the logbook itself does not carry much practical value other than historic trends which help somewhat to gauge the health of the engine.The logbook is also useful (or harmful) in legal offense and defense and provides a method for the FAA to pursue enforcement action should a maintenance practice be documented to be non-compliant to the FAR's.

As you have found, it is quite easy to evaluate the health of the engine and continue to monitor operating trends without any previous history.An engine can have a remarkably complete set of logs and yet suddenly make metal hundreds of hours before TBO.Conversely, logs can be conveniently lost to disguise a know problem, a prop strike for instance.Logs are a point of reference, not the absolute guide to engine health.A periodic physical inspection of oil consumption, oil pressure and compression will yield the best data as to whether the engine is airworthy or not.

Harry


Engine Stumbles at Moderate RPMs

Hi Harry:I have a C85 with Stromberg carb (20 hours on the overhaul on both engine and carb). The engine 'stumbles' when passing through 1500 RPM.Idle and top end are fine. Any ideas?

I just solved this problem with the A-65 installed in my Champ, but I changed several things, so I am not sure which particular change made the difference.

My problem was a very predictable stumble at 1300 rpm.The dead spot was very pronounced when the throttle was advanced or retarded in that range with medium or low authority of throttle movement.If I moved the throttle quickly, the stumble was there, but not as noticeable.However, I also had some backfiring in the exhaust when the throttle was retarded, which was a clue that the carb mixture was set too lean.

I enrichened the idle mixture in progressive steps, but the dead spot problem persisted.During my experimentation, I changed the airbox.The old one was extremely worn and was probably pulling a bit of air in from the warm side of the flapper valve.During the airbox change out, I changed to a new air filter, adjust the linkages, and, while the cowling was off, enrichened the idle thumbscrew.So, several things were changed at one time.

However, the stumble was noticeably diminished and I kept turning the idle mixture thumbscrew in until the stumble disappeared and the backfiring stopped.

Two more wrinkles in the control for solving this problem:I did not keep track of how far I turned the idle screw, so it could have been turned 1 to 3 turns- I have no idea.I kept adjusting until the problem was cured.Second, I started my troubleshooting when the ambient temps were 85F and completed them when the ambient temps were 50F.Did the change in temperature have an effect on the stumble?I don’t know.Maybe the stumble will re-occur when the temps warm up.

So this leads me up to answering this question in my least favorite way:with an unscientific hunch with no solid proof to explain my rationale for fixing the problem.

My thinking is that the carb was running too lean in the idle mixture and the transition was too abrupt from lean to rich as the butterfly valve opened and let more air pass through the carb venturi.As the butterfly opened more, then the fuel flow caught up and the stumble was remedied. Since I have enrichened the idle circuit and tightened up the leaks in the airbox, the engine has run significantly better.It idles perfectly, doesn’t stumble, no backfiring at all.It starts entirely predictably in ambient temperatures ranging from 90F to, currently, 17F.I would like to prove that the engine will stumble in that 1300 rpm range when the carb is too lean, but that would require me to fiddle with the mixture setting.To be honest, it is running so well that I don’t want to monkey with it at this time.

So, locate the slotted thumbscrew on the back of the carb where the carb flange meets the intake spider flange.Turn it in ¼ turn increments counterclockwise to richen up the idle circuit.As the idle mixture is changed, the physical idle stop set crew may need to be adjusted to keep the throttle closed idle correct.In a perfect world, when the ignition switch is cut off, the engine should run up 25-50 as the engine leans out when the last bit of fuel is burned up.I have found that achieving or detecting this rpm rise is really difficult with the Stromberg carb.I have attached a PDF copy of the Stromberg carb manual.Don’t do any work to your carb until you read this.By the way, unless this is an experimental aircraft, an airman with the proper rating, namely an A&P, should do the work on the carb

If the above fails, then the transition circuit from idle to cruise rpm may be obstructed.If you look into the carb throat, there is an extremely small hole just above the butterfly valve in the carb throat which opens up a circuit from idle to mid-range power.If this passage is obstructed, then the carb will stumble as the throttle is advanced through the 1300-1500 rpm range.DO NOT use compressed air to blow through the passage as you run the very likely risk of pulling a sudden vacuum in the float chamber and the float can implode or distort.The most correct way to clear this passage would be to disassemble the carb and try to clear out the passage with an ultrasonic cleaner.

Kind of a long explanation, but try enrichening the idle mixture and see if you can force a change to the stumble.

Harry


O-200 Timing For More Power/Cylinder Selection

I wrote you a year ago or so with oil questions regarding our low time A150. 470TTSN We continue to monitor the oil issues and at this point we are ready to some more work on the engine. The plan is to pull a cylinder and look at the cam and see what it looks like. If we get past the cam the plan is to replace the cylinders with new units. I could use some suggestions on which way to go. Before we do that however, I would like to confirm that after we do the top end with new cylinders that we can at that point, advance the mags back to 28 from 24 per the AD and get some power back. If the timing has to stay at 24 we can live with the current cylinders until we see further deterioration in the rings and valves. 

Superior or ECI cylinders is a point I could use some advice. We don't plan on keeping this plane forever, but it still needs to be done correctly. I like the nickel ECI and could use a screw in cylinder head temp receptacle, but the cost is pretty high. I believe the ECI units have the cylinder head temp probe as a screw in probe.

The other point I need advice on is the ignition system. One mag is the venerable 4001( original 1975 install, 470 TT), and the other is a 4003 installed 1993, (280TT). The harness is original and looking pretty tired. After the annual last month having flown it about 10 hours we developed a very slight, continuous, backfire at reduced power (1500RPM in the pattern). The 500 hour mag inspection is basically due. Replace with a complete system from Spruce or Chief? Overhaulthe 4003 and replace the 4001 add a new harness?

I seem to remember that you found a very low time since new Aerobat and you were working to put it back into service.

Here is a link to a TCM Service Bulletin which details magneto to engine timing:http://www.tcmlink.com/pdf2/MSB94-8C.pdf

The pertinent few lines to this conversation can be found on Page 6, Note 5. Depending upon the part number or revision of cylinder, timing may be set at 28 degrees.All new manufacture cylinders from TCM, Superior or ECI can operate with 28 degree timing.Additionally, some older cylinders may operate with 28 degree timing, so check the part number of your cylinder with the numbers listed in the SB above.The AD was a bit complicated and many mechanics complying with the AD took the simple route and changed the timing without looking at the cylinder part number.

In reality advancing the timing back to 28 degrees is not a significant change.You will notice a slight improvement, but you probably are not going to gain 100 fpm extra climb or 5 mph cruise.The timing change provides a very subtle improvement.

My opinion is that if there is nothing wrong with the existing cylinders, continue to operate them for as long as you can.They are virtually new, so there is no reason to expect that they wouldn't provide nearly 1000 hours of service.Personally, I'd use the money you'll spend on new cylinders into gas or avionics upgrade before I'd junk the cylinders.

Otherwise, my preference is factory TCM cylinders as I have had best success with that type over others.The Superior cylinders are a bit heavier, and the ECI seem to be equivalent in price and performance to the OEM TCM.I have had more success with the warranty for the TCM cylinders. Superior and ECI are simply smaller companies and more cost sensitive, so I have to struggle a bit more to get warranty consideration.Historically, fancy coatings on cylinder walls have not been a long term benefit.Unless you are operating in a highly humid environment, plain steel cylinders will work well.

The magnetos, however, are a bigger problem.The 4000 series are life limited by a Slick Service Bulletin (not an AD) to 800 hours total time. From the practical standpoint, the 4000 series is a problem in that the magnetos are "sealed units" not capable of being serviced and no parts are available.Generally, a real inconvenience to get serviced should a problem occur.

Which leads to the real problem with your installation:the 4001 is the correct magneto, but the 4003 is not a legal installation.The 4003. In fact, was approved for an A-65 engine, and was originally a RH rotation device, not the LH required for the O-200.I'm assuming that the original 4001 failed, no parts were available, and some enterprising soul illegally cobbled together a repair using the 4003 magneto.Not legal and not safe as the 4003 will not operate properly when the rotation is reversed.

The complete ignition kit for the O-200 is the Slick K4520-40 which will include new manufacture mags, harness, spark plugs and installation gaskets. The new 4301 magnetos can be serviced and parts are readily available.

But, the 4000 series magnetos are no longer accepted as cores, so you will have to pay an extra $300 unless you can find some suitable cores.Spruce is a direct distributor for Slick and offers great prices.Check out Chief, Air Power and Mattituck, also.

Harry


O-300 Performance Mods & Compression Ratio

I plan to rebuild an 0300 and would like a little more performance than stock.My idea was to have free flowing tuned exhaust, one electronic mag and one stock mag, stock camshaft and stock carb. 

My question is how much compression can I increase over stock and still be able to run 87 octane?

The engine will be run pretty much as it did when it was in the 172, i.e. about 2300 rpm cruise and no faster than 2700 rpm. One of the problems with answering questions on experimental engines is there is no reliable method to forecast or measure performance unless the engine is run in a dyno.Remember, you are experimenting, so there are no guarantees once you depart from a known, proven stock configuration..

Generally speaking, regular auto fuel will run ok up to 8.5:1 compression ratio.A qualifier here, though, is that effect of the reduction in atmospheric pressure begins at about 3000 feet and pressure decreases rapidly above 5000 feet.The point is, 9.5:1 pistons may work well on regular fuel at 5000 feet pressure altitude due to the degradation of ambient atmospheric pressure.From the practical standpoint, any compression ratio higher than 8.5:1 will require higher octane fuel.But, I stress, I have done zero empirical testing other than monitoring engine temps, so I truly have not idea if this CR is reliable in the long run.

You should contact Ken Tunnel at LyCon Rebuilding in Visalia, CA, 559-651-1070, or visit www.lycon.com <http://www.lycon.com/> .His company has a lot of experience with modifying engines and they are also the only game in town for high compression pistons for the O-300.Ken will have much more practical experience than me.

The exhaust is pretty easy- straight pipes are neutral and neither add to nor detract from engine performance.Six individual pipes with the outlets bunched together will result in a sound nearly exactly like a Merlin.My Globe Swift has six individual pipes and I get comments all of the time that the engine sounds like a Merlin.

Remember, if you modify the engine, the FAA requires that the data plate be removed as the engine no longer conforms to the type certificate.

Harry


Crankcase Cracks

Harry, do you know if a Continental IO-360 can be repaired if there's a 3" crack around the case?  Specific location is where the case starts to flange for the cylinder mounts.

The best thing to do is to send the case to a shop which specializes in case repair, such as Divco in Tulsa, OK.  Check out www.divcoinc.com/.

I know that some types of cracks can be repaired, but I have no idea what the criteria is for determining the limits of what can and cannot be repaired.

Harry



Messages January-May 2008

Running Cool in Winter

Harry, once again I find myself turning to your thoughts and advice. I have a C90-8f engine installed on my J3 cub. I had two cylinders loose compression after the install. The folks at Don's Dream Machines who built it up for me had me send the cylinders in for them to look at them. They could not see anything wrong so honed them and put new rings on the pistons.

I am still getting oil out the crankcase breather leaving large puddles. I did a compression check cold and hot and have good compressions now but I am now getting some blow by through the exhaust valve on the number 4 cyl that was ok before. I am worried that my engine is not getting up to temperature and this might be what is causing the problem. I checked the current temp gage against a candy thermometer and found my gauge reads 10 degrees higher than the candy thermometer. This means when flying my cruise temps are only 140 degrees. I have tried flying a quart low at 4 quarts to see if I could increase the temps. This helped just a tiny bit. In a sustained climb to altitude I can only get to around 175 degrees on my gauge which means 165 degrees compared to the candy thermometer. Do you have any ideas what I could do to increase the temps. I have blankets on the oil tank and on the intake tubes. I even ran these when the weather was warmer with no real increase in oil temps. Any ideas?

What does staking a valve mean? The guy I got the engine from says I should have a mechanic stake the valve to see if that helps. I asked if he wanted me to send him the cylinder as it is still in warranty. I am waiting to hear but with him in Georgia and me in Oregon I am not sure if I should try this myself or send it back to him. Any ideas or help you could give me is always greatly appreciated.
 

Because the Cub cylinders hang out in the breeze, you will never get much past 140-150 F in the winter.  There is simply too much cool air and no way to trap the heat in the engine compartment, period.  However, this is the way the Cub has always been for 75 years, so some sort of solution must exist.  The best group to ask is the Cub Club as the collective experience of hundreds of Cub pilots can be consulted.  Clyde Smith, the Cub Doctor, is probably the single best person to ask about this problem.

I had the same problem with my Champ, but I installed a block off plate to reduce airflow through an intake hole just below the prop.  I also installed a block off plate at the bottom, rear of the cowling which restricts the outflow of cooling air.  The heat of the engine simply stays in the cowling to keep the engine warm.  The open Cub cowling presents some real problems with retaining heat, though.

Staking a valve refers to reaming the valve guide to remove carbon.  Carbon can keep the valve stem from sliding in the valve guide.  Sometimes this process involves creating an internal knurl on the ID of the valve guide to raise up the valve guide surface to tighten up the operating clearances. I'm not sure of the actual history of the term staking, but a common sheet metal tool is a spike looking thing called a "stake".

Harry


Lower-Cost Exhaust

I'm building a Pober Pixie, and have an A-65 for it.  I absolutely   love the sound of a Cub and figure that the best way to get it would   to put a Cub exhaust system on the plane.

But the certificated ones are quite expensive (I'd like to stick to stainless steel.)  Do you know anybody that could build a non-  certificated "Cub" exhaust, with muffs, at a more reasonable   "experimental" price?

Anything labeled "Cub" commands a premium, no way around it.  The Cub exhaust has a lot of individual parts, and is labor intensive and, experimental or not, is expensive to make. Your best source will be Wag Aero www.wagaero.com or Classic Air Ventures http://flyoldplanes.com/ for a Cub type exhaust.  In any case, a complete Cub exhaust complete with muffler and heat shrouds will be $1100-$1500 or more.

If you want a more reasonable exhaust, the Aeronca type is the way to go.  A pair of steel exhaust stacks for an Aeronca is about $350 and a heat muff for the carb heat is about $100- more than half the cost of a Cub exhaust.

Harry


A Carb Saga... Is is Ice, or?

The plane's uilder mentioned he swapped the Stromberg carburetor for a Marbel Shelby (MA-3) since it iced up routinely on some run-ups, take offs and I think also in flight.  The MA-3 is large, I think too large for the A75 according to my friend the builder, so it tends to load up if in idle or taxiing too long.  Usually can clear it out with full run-up RPM, but sometimes may need to clean lower plugs.

Last time, while awaiting a landing aircraft, I did a left mag check and it back fired (at least sounded like it) 4-5 times, I tried to  clear it out and did mag check again and it did the same.  Finally seemed to clear out so I took off.  I'm a student pilot so still learning quite a bit and truly enjoy it.

Just wondering, why would the Stromberg ice up so readily if it was made for the A75 I believe and any thoughts on the recent back firing?

I am not aware that the Stromberg is any more susceptible to ice than the  Marvel Schebler.  In any case, the carbs were swapped, and it sounds like performance problem continued despite the carb change, which tends to discount the carb as a problem.

I wonder if the problem is with the magnetos and not the carburetor.  When the engine roughness or backfire occurs, does it occur when the magnetos are selected individually to left or right?  If the problem happens on one  mag, then it is likely a mag problem.  Your description seems to indicate that the left mag is more of a problem.

If the mag electrical circuit is breaking down, then the plugs will foul  and the engine will certainly backfire.  Carbs tend to cause a backfire with a too lean mixture, not too rich.  However, if there was enough fuel in the exhaust, it could ignite in the exhaust, but the plugs would probably be  extremely sooty along with sooty deposits from the exhaust.  If the mag  misfires, it is very common to get a backfire and rough running throughout the rpm range.  It is very unlikely to get carb icing at cruise rpm as the vaporized fuel will overcome the icing potential of any ambient moisture.

There are MA-3 carbs approved for the A-75- the correct part number for the A-75 is 10-4233.  The 10-4894 is for the O-200 and could cause problems if installed on the A-75.  Check the carb dataplate or the mounting flange for the part number.

Another possibility is that a valve is sticking or a hydraulic lifter is collapsed.  A sticking valve will cause a backfire, and will backfire with either left or right magneto selected individually.  Because the engine backfires on both magnetos, this condition is frequently incorrectly  diagnosed as a carb problem.

Harry

Follow-Up #1

Thanks Harry.  I was wrong, the carb is a MA3A (that may make a  difference).  Unfortunately, the plane is near ATL GA and I'm in Tampa FL.  I flew it last weekend for the first time.  Slick mags were installed a year ago and it sat in Tampa for the last year while I tried to fix a cracked canopy with no luck - I'm not very good  mechanically.  My buddy/builder took it back to GA to sell it for me, but after he fixed the canopy, and did some work on the engine, I asked if I might fly it and see if I wanted to keep her.  She flew 122mph @ 2300 rpm on a cold day.  A lot of fun.

So, I'll check on the part number and hopefully sort out the back fire, rough idle/fouling plugs and former icing problem.  Don't think it's iced since the new large Marvel Schebler was put on.  I don't  recall the back fire occurring with the right or both mags on, it was getting dark and I was happy to be back on the ground and wondering how to get back to my buddy's grass strip with no cell phone and no lights and back firing engine - it has no electric system as you probably know.  Needless to say that's another story and I'm lucky to have such good pilot friends.  They were as happy to see me as I them and will never leave the ground without my cell phone again :-)  .  I couldn't apologize enough to them.

The MA3 and MA3A are the same carb.

No problem if you have further questions.  The engine problem can be  isolated through careful troubleshooting.

Another idea on the mags is that the left one may be timed to the engine incorrectly.  Given that you are not mechanical, the following description will read like a foreign language, but you can save this to pass on to a  mechanic who will get it.

The Slick magnetos used on the A-75 are Right Hand rotation.  In the distributor block are holes in which a timing pin inserts to correctly position the distributor finger to fire at the correct distributor tower.  The holes are labeled L for Left and R for right, which corresponds to the rotation of the magneto, not the placement of the magneto on the engine.

So, both magnetos for the A-75 need to be pinned using the R holes.  If the  L hole was pinned for the magneto on the left position, the engine is certain to run, but backfire badly as the distributor gear is out of synch with the firing order.  The way to fix this is to physically remove the  magneto and re-pin and install back onto the engine.  DO NOT just check the opening of the contact points to the engine.  The contact points can open at the correct firing point, but the distributor gears can be out of synch.

Another possibility is that the two spark plug leads on the top, left side of the engine are switched front to rear.  The Number 2 for the front cylinder sits closer the to the rear #4 cylinder, and the #4 mark for the  rear cylinder sits just aft of the baffling.  The cylinder nuts will be marked for T2 for top #2 and T4 for top #4.  Due to confusing cylinder marking on the engine, these leads frequently get switched front to rear.

Like I say, this may not make any sense to you, but save this e-mail for future troubleshooting.

Harry

Follow-Up #2

Well, I found out the carb is for the 108hp engine, not the A75.  My buddy thinks the Stromberg has a smaller venturi or something and is much more prone to ice.  Do you think there are any concerns with using the larger carb?  According to my friend, it will cost 1200 (400 for the core and 800 for the carb) to get the right size MA3A if I can find it.  The larger carb has iced one time I think, but carb heat did the trick.

Given that 12,000 A-65/A-75 engines were built between 1938 and 1948 using the Stromberg carb, and the fact that there are probably 4,000 engines with the Stromberg carb still in service today, the weight of numbers suggest that the Stromberg does not ice up on every engine and provides reliable service.  I have probably 800 hours or so behind Strombergs with no real problems.  If the Stromberg carb performed as poorly as you describe, then this series of engines would have a horrific accident record.  As it is, the A-65/A-75 series of engines has 70 years of successful operating history, and 95% of these engines flying today are equipped with the Stromberg carb.

During the design of the carb, the venturi is sized for the engine intake flow requirements.  The A-75 is 170 cubic inches and the Lycoming is 235 cubic inches.  The carb installed on your engine is not optimized for your engine- period.  Given that your engine is not running correctly, it can be surmized that the wrong carb is affecting performance.

I'm going to be very blunt in that you keep describing troubling engine performance with an engine equipped with the wrong carb.  I personally would not fly a plane with the problems you have described until I found and solved the problems which are causing the backfires and loss of rpm. Something is wrong and the best way to start to sort out the problems is to revert back to a known baseline.  Whether the Stromberg is more prone to ice or not, it is a known quantity on the A-75, whereas the carb for an O-235 Lycoming is not.

Regarding the "icing" condition, I think that this is an unlikely situation. In the grand scheme of things, carb ice does not occur with regularity as the relative humidity and temperature has to be just right.  Carb ice tends to develop at reduced throttle settings, but rarely at cruise.  The Florida/Georgia climate, in particular, is not conducive to carb ice forming during cruise.

I would strongly suggest that you contact Don's Dream Machines at Griffin,Georgia (www.donsdreammachines.com).  Don Swords has a lot of experience with the little Continentals and can probably sort out your problem quickly.

Harry

Follow-Up #3

(First Message):
Could you tell me what the expected problems are with using a larger carb on an engine than spec'd for, other than loading up the engine.  I find some people saying it's not a problem other than accounting for the richer flow by not letting it run at low rpms too long. My concern would be if it will result in damage to the engine causing it to fail, e.g., blows a piston or cylinder I guess due to too much combustion - though I don't know if that's the case.  Appreciate any thoughts.

BTW, my friend installed the mixture control to allow burning soot off the plugs if it does begin to load up.

Otherwise, guess I'll send the stromberg to Don Sword though I know my buddy will be unhappy with that decision.

(Second Message):
My friend has decided to try and convert my existing Marvel Schebler MA3A carb (made for the O-200) to a MA3APA (made for a continental A75) by buying the MA3APA's parts for the MA3A carb core I guess.  Hopefully this will work.  Don Sword said he'd look at the Stromberg for me, but my buddy thinks he can make the Marvel Schebler work and doesn't want me to use the Stromberg since he tried three and they all iced.  Do you think the Marvel can be converted?  Thanks again.

I have really been struggling with how to provide any more advice to you. I think that you guys are just simply going in the wrong direction with your carb troubleshooting.  To be blunt, the carb changes which you are trying to make to this engine simply seems like an accident in the making.  You have a sick engine and your friend is trying to cover up the symptoms instead of curing the ailment.  Your buddy might be well intentioned, but it seems like everything he does makes the engine run worse.

You'll have to consider my point of view.  The little Continentals are very simple engines.  In their stock form, if the components are in good operating order, the engine will run reliably with the Stromberg carb- period, end of story.  99% of the A-75 Continental engines in service use the Stromberg carb, and have done so for more than 60 years.  Arguably, the Stromberg may be the single most successful carb in aviation history as I am not aware of any lawsuits which have named the Stromberg carb line (there are plenty for the Marvel Schebler).  So long as the engine, magnetos and carb are in good repair, your problems will be solved if the engine is configured to a standard, stock configuration.

Your friend is going to think I am an idiot, but 99% of the historical experience with the stock engine and carb over 75 years is in my favor. I'll gladly be the fool backed up by these kind of statistics.  You have a sick engine and you really need to get a licensed aircraft mechanic involved to sort out the problems.  Don Swords is as knowledgeable as anyone, even more than me, so working with him is a good thing.  I am positive that if you get a guy like Don involved, and let him completely handle troubleshooting the engine, the problem will get solved.

I apologize for the blunt answer, but it is to the point where I have to call it as I see it.

Harry

[RJW Note:  I've been flying Moonraker for about 14 years now.  I've got the Stromberg, and have never had an instance of Carb Ice...]


Cutting the Clutch Shaft on a Starter Conversion

I have a Cessna 140 with an 0200A and thinking of replacing the pull starter with a push button starter.  I'm a little confused as to the bolt on statement.  Does Sky Tec's starter just bolt on out of the box without cutting off  the clutch shaft?  Sky Tec seems to indicate you do in their internet description. Hope you can clear up the confusion.

Replacement of the pull type starter requires that the engine be modified. The biggest modification is to cut the shaft to which the pull starter clutch mounts.  The modification can be found at this link: http://www.skytecair.com/Converting_Pull.htm

The Sky Tec O-200 starter mounts with no modifications only on engines which have been previously modified or were equipped with key type starters.

Harry


Continental GPU Parts

I bought a Continental GPU for parts for my project. I was told it was  a C-90 GPU but I have not been able to find any info on that engine.

It has the accessory case with mags, C-90 starter opening and generator. The cam shaft is numbered 537U107 and it looks identical to a C-90's.  The rear case is aluminium. The cylinders are identical to any  Continental of that power range.

I would appreciate any informations on the history of that engine.

Most of the GPU engines I have seen are significantly different than the aircraft versions.  The cylinders have a top mounted intake instead of the bottom mounted intake and exhaust of the aircraft engine.  The case is usually set up for a bed type mount as opposed to a rear mount of the aircraft engine.  Usually the GPU engines are set up for single ignition. The crankshaft of the GPU lacks the centering cone for the prop and the large prop bushings.

If you have a GPU engine with dual ignition and down intake/exhaust cylinders, then I am not familiar with it.  I have a couple of the PE90 engines, but they have all of the differences I have noted above.

I'm not going to be much help, but here is a link to a picture of a PE90 engine:

http://www.vortechonline.com/specials/Continentlengs.htm

Maybe the company at this page can offer more information.

Harry

Follow-Up

That is what I have for sure. We were able to use several parts, like cam, rear case, connecting rods, bearings to build up a C-90.

If you know, was it a 90 hp or 150 hp as a GPU and in what period in the past were they used, I supposed by the military and for which aircraft or military vehicle.

Continental manufactured two types of four cylinder GPU engines which were kind of aircraft derivatives:  The PE90 and the PE150.

The PE90 looks like a four cylinder Continental except the intake is on top of the engine.  Lots of the internal bits like the lifters, hydraulic units, rods, pistons, gears, etc will drop right into the C-85 through O-200.  The crank can be used, but the prop flange is thinner than an aircraft unit and needs to be converted to use the internally threaded studs for the prop. The prop centering taper is missing, so the flange studs take 100% of the load.  Aerobatics are discouraged with the GPU crank.

The PE150 is a slightly different engine.  It is bigger and uses what appears to be cylinders derived from the O-470.  I can only guess that this engine uses a bit more parts from the 470 family, but I'm not sure.
I took a look at the link I sent to you about the PE90 engine.  The pictures indicate that this engine is actually a PE150.

These engines were used as power supplies or in engine start carts.  There must have been quite a few manufactured, but I have not found a whole lot of information.  On the other hand, I haven't really spent much time looking as my focus is primarily the aircraft versions of Continental engines.  I just buy the GPUs for parts, also.

Harry


Finding a GPU Engine

Any idea of a good place to locate a 200 gpu?

There is no central place where you will find engines sitting around- at least to be bought cheap.  The GPU engines are kind of few and far between. Without question, the O-200 is still very easy to find.  The easiest source are either salvage yards or engine shops as they will have engines on the shelf.  Also, simply scrounge the want ads at www.barnstormers.com, www.trade-a-plane.com, and all of the owners group sites which use engines in the horsepower range you need.

I find that engines are readily available, but most of the buyers are looking for a $500 core, when most core engines are in the $2500 range.  So, the real problem tends not to be availability, but the dollars that we are willing to spend to buy an engine.  The last $500 core I bought was in 1979! Nowadays, I figure that I am getting a deal for $1000-$1200.

Try searching Continental PE90 for the GPU engine.  There are a number of airboat sites which still have parts or classified ads which may include this engine.

Harry


Stumbling in Cold Weather

I have read many of your articles about A65 engines, carburetors and numerous other technical issues.  You are obviously an expert in this arena.  I am currently trying to gather as much information as I can before I dish out a bunch of money repairing a carburetor.

I own an Aeronca 11AC with a reassembled A-65 or 75 depending on who you ask.  The guy I bought it from had the cylinders chromed and put new eismann mags and numerous other upgrades to the motor. I don't know the particulars, I'm more of a flyer than a mechanic.  The old timers here in Ponca City, Oklahoma keep it flying for me.

My issue now is that the engine stumbles, epically in cold weather, below 1500 RPMs.  It doesn't matter if it cold or warm and is only slightly improved with carb heat.  Once above 1500 it runs like a top. It stumbles in level flight the same as on the ground.

Carburetor is a Marvel-Schebler MA-3.

I'm a realist and I know that this problem won't fix itself however, I don't want to throw away money on a $900 rebuild if not needed.  Could this just be something clogged somewhere inside the carburetor?  Do I need to change the jet?

It could be that the idle bleed air circuit is obstructed.  The most reliable way to fix this problem is to soak the carb in an ultrasonic cleaner.  You really don't want to use compressed air to blow out the passages as you can create a negative air pressure in the float bowl and collapse the float.

Another likely problem is that the idle circuit is too lean.  I have noticed a very common problem of the Stromberg kind of stumbling in the 1300-1500 but running pretty good in the rest of the range. The engine will usually backfire a bit when the throttle is reduced through this range.  If this happens, then  the idle mixture is probably too lean and needs to be enrichened.  The Stromberg manual says that the idle circuit only operates up to 900-1000 rpm, but I have noted that when the mixture is too lean, the carb simply starves for a second or two until the automatic mixture circuit of the Stromberg can compensate.  The idle mixture screw head is slight smaller than a dime and located at the aft, upper flange of the carb where it meets to the intake spider.

Your comment about the condition improving with carb heat supports the lean running theory.  When carb heat is applied, the mixture will enrichen slightly as the air molecules will expand faster than the fuel molecules. The net result is that there will be a slight higher fuel to air molecule ratio when carb heat is applied.

I have also attached a copy of Continental Service Bulletin M64-6.  This Bulletin specifically addresses idle problems when operating in cold weather.  The solution is to make a baffle which is mounted in front of the air filter and prevents the intake from cooling too quickly.

As far as fixing the carb goes, you will need to be a rated A&P mechanic or work with an A&P.  It is impossible to guess what the problem is unless it is put on a workbench and inspected.

Harry

Follow-Up

Fabricated and installed the baffle this afternoon.  It corrected the problem!  I now have no hesitation.  I lost  750 rpms on the top end but all the old timers around here say I was pushing it to hard anyway.  Aren't you suppose to run it wide open all the time?  Just Kidding I usually cruise at 2450, the guy who rebuild it and calls it an A-75 says the 2450 is no problem but the other guys with the A65 are afraid that my little engine is going to eat itself one day.

Flew it from Oklahoma to Blakesburg, Iowa last summer at 2450 with very little oil usage and she ran like a top.

I can't thank you enough.  It wasn't super cold (45) today so I went to 4,000 feet where I knew it was colder and still no hesitation.  I can't wait to see how much difference it makes on a really cold day.

Wow....Wow....Wow......

ChuglyThanks for the nice words, Chris.  I seldom get any replies back as to whether or not my suggestions actually solve any problems.  I was just out this morning doing some ski flying in 30F weather and some of the guys in the group had the block off plate and swore by it.  I don't have one and my engine runs great, so go figure. Given that your tach is reading accurately, it sounds like your plane is operating with a climb prop.  The climb prop usually shaves a sold 8-10 mph off of the cruise, which makes it more likely to cruise at a higher rpm to have any sort of good cross country speed.  My Champ has a climb prop and I cruise at 75-78 mph while other Champs do about 82-85 with a standard prop.

The engine Type Certificate Data Sheet (TCDS), which is the FAA certification for performance limits for this engine, lists some interesting details:

For a 75 hp engine, the sea level pressure, five minute limit is 2275 rpm. The sea level pressure, max continuous limit is also 2275 rpm.  So, at 29.92" you can run the C75 all day long at 2275 rpm.  The C85, which has the same reciprocating section as the C75, has a 2575 rpm 5 minute climb/continuous cruise limit.  Interestingly, the A-65-14 is rated at 75 hp at 2675 rpm, and also has the same reciprocating section common the 65-85 hp engines. 

There are some differences in the crankcase and crankshaft of the O-200, but the bearings are about the same, if not identical, as the lower hp engines.  The O-200 can be legally turned up to 2750 rpm.  So, if you ignore the TCDS limits, you can draw the conclusion that the bottom end of the C75 can handle the extra rpms.

I've attached a photo of Chugly, my ugly Champ on skis.  I usually take my Globe Swift to the Blakesburg and Brodhead antique fly-ins during the late Summer.  I'm always at Sun n Fun and Oshkosh exhibiting with my company,  Gippsland Aeronautics, so look me up if you are the shows.

Harry


C-85-8 vs. C-85-12

I have a Air knocker with a C-85-8. I believe I need to convert this to a -12 configuration to mount a starter. What parts are involved other than changing out the accessory case using one from a C-85-12,C-90.or a 0-200?

The C-85-8 and C85-12 engines are significantly different.  The crankcase, accessory case, accessory gears, and magnetos are different, among other details.  The hole spacing and pattern on the -8 accessory case is different than the -12 case, so the -12 accessory case does not bolt right up to the -8 crankcase.  I am not aware of any approvals to convert from a -8 configuration to -12.  The good news is that your engine is quite desirable, and the C85-12 is not as popular.  The -8  is so desirable that there is an STC to convert -12 engines to -8 status (but not the other direction).  You would be money ahead to sell your -8 and buy a -12.

Unfortunately, there is no easy way to install a starter on the -8 series engine.  I have looked at several methods, but the expense and complexity of the conversion is simply too high.

I'm converting my Champ to a C-85-12 (but no electrics) and I'm using the Lasher STC because it provides the least amount of restrictions for engine choice.  The Lasher STC works for the C-85 series of engines, but not for the O-200.  You will need some factory drawings and an entirely new cowling to legally install the O-200.

Sorry I don't have a better answer, but this is the straight story.

Harry

Follow-Up

You are suggesting to me that the -8 engine is a better engine than the -12. Did I understand this correctly?

I guess the -8 engine could be lighter, therefore has a better hp to weight ratio.

The -8 is preferred because it is lighter than the -12 and less complicated. Internally, the two engines are similar, but the electrical accessories, wiring and battery adds a lot of weight and reduces engine power output a bit because the mechanical drag of the accessories eat up a couple of horsepower.  Also, within the Cub and Aeronca groups, there is a certain feeling that the -8 is better.  Most of the guys who think the -8 is better really don't know why, it is really just what they have "heard".  The -8 is also a more historically accurate engine for the more perfect restorations.

However, it is all a point of view.  If you want electrics, then the -12 is more valuable.  If your preference is simple and light, then the -8 is a better engine.  Basically, they are both 85 hp engines, the -12 is about 5 lbs heavier, plus the added weight of the generator, starter, battery, battery box, wiring, etc which adds another 30-35 lbs or so the airframe.

I split the difference by building a -12 minus electrics, which is an approved installation.  My engine weighs about 5 lbs more than a -8, but I do have the option of installing electrics at a later time.  I probably won't as I don't mind hand propping my engine.  Maybe in 20 years I won't, but that is a way off yet.

If you are not on the lists, join the Fearless Aeronca Aviator list and the National Aeronca Association discussion.  These two groups will have a ton of information on the pros and cons of the -8 vs the -12 installation in terms of impact on aircraft performance.

Harry


Induction System Improvements

Have just stumbled across your Continental web page, I was quite amazed at the depth of your knowledge and willingness to share it.

I have question regarding the 0-200 installed in my Vari-eze and hope you might be able to advise.

I have recently installed the Dynon EMS D10 which has the ability to monitor all engine parameters. Previously an Electronics International single EGT/CHT.  As I suspected the spread of EGT's and point of peaking each cylinder is horrendous. I had seen reference to an 0-200 graph in John Schwaner's manual Skyranch Engineering Manual where there is a comparison of EGT's with a standard (?) induction system and then also overlaid with the plots of the EGT's with a flow straightener device installed, much much better. .

The Vari-eze has the standard filter/heat box, which I have heard is not the best for even induction, and I will be looking at this area. The carburettor is the std MA-3 single venturi, I am curious to know whether returning it to the pre AD of dual venturi is advantageous and or wise? The exhaust system is a pretty typical Vari-eze exhaust, 2 into 1 each side. Various selections of carb heat don't seem to help but it does shift the numbers around, similarly differing throttle settings do much the same. I am only able to peak 2 cylinders as engine roughness is so bad that I give up and enrichen.

Typically I run WOT from take off till TOPD using altitude to vary the power by operating between 8500' to 13500'

I would like to improve the induction system so as to achieve a smoother running more efficient engine, any advice on the flow straightener device or perhaps a Hiclone swirl device, or any other thoughts would be greatly received.

Below are some numbers from previous flights.

PH 9500'    DH 11300'                                        PH 12500 DH 13500
OAT 14c    QNH 1013                                        OAT 3c QNH 1013
RPM 2390  MaP 17.7" (not WOT)                        RPM 2670        MaP 18.5"  (WOT)
Oil P 43     Oil T 154                                           Oil P 46 Oil T 148
FF 16.3 L/hr                                                       FF 18.75 L/hr
    CHT        EGT                                                   CHT EGT
1. 350         1428                                                 381 1426
2. 350         1167                                                 397 1317
3. 382         1360                                                 383 1310
4. 370         1315                                                 337 1183

These new engine monitoring devices are fantastic in that more data is available to the amateur pilot now then when the engine was originally certified!  Most homebuilders probably have more raw engine data than the OEM.

To be honest, I don't really know if a flow straightener will work or not work.  In the experimental world, it simply boils down to trial and error until a solution is found which works.  I have built O-200 racing motors, but each one was unique and not all of the techniques which were successful on one engine was successful on the next.  This is one reason I tend to keep most of my dialogue limited to stock configuration issues as I can prove performance and reliability issues, whereas with experimental issues I can't.

Without a doubt, the single most knowledgeable person about the O-200 as installed in a Vari-Eze is Klaus Savier.  He has literally spent thousands of hours fine tuning his O-200 for maximum efficiency and has probably figured every angle of this engine for improvement.  Here is a link to his website:  www.lightspeedengineering.com .  I'm not sure if Klaus will offer much advice, but he is a personal friend of mine, so feel free to drop my name to open the door.

A comment on the stock two-piece venturi vs. the current one piece.  Airflow through the carb reacts differently to the one piece, and many operators reported power losses with the one piece venturi.  A solution was a "pepperbox" fuel discharge nozzle which helped to atomize the fuel better. Although I can't find any solid documentation, it is my understanding that the two piece venturi had a few more sharp edges, which helped to swirl and atomize the fuel better. 

Generally, the field consensus seems to be that the two piece venturi simply works better.  The FAA actually amended the AD affecting the two piece venturi:  The original version of the FAA AD mandated replacement to the one piece.  There were so many complaints of poor operation that the AD was amended to leave the two piece installed, but more frequent inspections were required.

Airflow through the intake is a balancing act.  If it is too turbulent, then it becomes inefficient.  If it is too straight, then the fuel may not atomize properly which also results in inefficiency.

So, I don't really have a pat answer other than you will have to do some experimenting.  As a bit of a shortcut, contact Klaus to see if he has an answer based upon a couple of decades or more of experimenting with the O-200 in a Vari-Eze.

Harry


Adding a Starter to a C-90-8

I bought an aeronca champ a bout 8 yrs ago in a basket. It has a C 90-8 in it. It was supposed to be low time, but to be sure, I tore it down. Good thing I did because it had issuses. My question is this, What does it take at this point to make it a -12 with a starter and where would be a good source of parts? I plan on putting it on floats and would be a lot handier.

I often comment that most claims about engine overhaul condition are questionable.  Time and time again I hear stories about engines which are "supposed" to be in great running condition and turn out to need work. Unfortunately, you are not alone in your experience.  Approach every engine like it is a rebuildable core and hope for the best.

While there is an STC to convert a -12 engine to -8 status, I am not aware of a process to convert from a -8 to a -12.  While the two series of engines share similarities, there are quite a number of differences, also.  First, the hole spacing for the hardware which mounts the -8 case and the -12 case to the crankcase are different, which means that the crankcase and accessory case are different between the -8 and -12 engines.  The next problem is that the accessory drive gears are different between the -8 and -12.  The gearing for the starter also reverses the magneto drive rotation, so the magnetos and ignition harness between the -8 and -12 are not interchangeable.  So, it boils down to replacing the crankcase, accessory case, accessory gears and ignition system.  Not an easy or inexpensive change.

However, the C-90-8 engine is relatively rare and highly prized by the Aeronca and Piper communities, so it has excellent resale value.   The C-90-8 is preferred because it is much lighter than engines with electrical systems and also a simple powerplant due to the lack of electrical system. It is the opinion of a lot of operators that the C90-8 is also the strongest pulling of the four cylinder Continentals, perhaps due to just the right combination of cam, compression and rpm. 

So, an option is to sell your C-90-8 and purchase either a C-85-12 or O-200 to get an engine with a starter and generator.  Depending upon condition, that C-90-8 will sell quickly and easily fund a good portion, if not all of  the cost of another engine.

Harry


Chamfering Cylinders

Hi, I'm rebuilding an O-200 for experimental use. I'm using C-85 pistons to get more power and understand that  a chamfer should be added to them for clearance.  I have millenium cylinders and I did a "dry run" in the cylinder with  putty on top in the areas that looked like potential interference. There wasn't any interference and it appears that there is about .070" clearance in the areas that look like problems.  Should I still chamfer? Will the pistons "grow" that much when at temperature to cause problems?

The combustion chamber of the Millenium cylinders is different than the stock Continental units.  Maybe there is more clearance for the C-85 piston- I'm not really certain.


The interference point is the edge of the piston crown and the radius of the combustion chamber.  The chamfered edge on the piston is not exactly a desirable feature as carbon can collect there and lead to cylinder scoring or possibly build to the point of interfering.  I have no idea how much the piston will grow, but .070 seems like a lot of room.  If you can operate safely without a chamfer, this is the best route.  However, you really need to look at the clearances to be sure that you have plenty of room.

I guess I don't really have an exact answer.  Experimental engines are just that, so expect to experiment to develop your own tolerances.  This is the reason I prefer to answer questions on stock engines- the results are more predictable.

Harry


Can't Get Oil Pressure

Hi: I sure hope you can help me. I have an A65 on my '46 J-3. Maybe 200 SMOH.  Runs perfect, high compressions etc.  Here is the scenario: Unfortunately this engine isn't run regularly.  During the annual, I changed oil but the engine had not been run for about a month.   I'm not getting any indicated oil pressure.  I have removed the oil pressure line from the right rear of the engine to eliminate the antique gauge and also the spark plugs (NO electrical).  Spinning the prop doesn't help.  No oil from the opening. In the past someone told me to remove the large hex allen plug from in the front of the engine (right side) and pump oil into the engine, put the plug back and spin the prop but that didn't help.  I really don't know what that does and how much oil do I squirt into the engine?  This problem seems to happen if we don't run it up every week or two. My guess is that the pump is "cavatated", lost it's prime, or just isn't working.  I'd like your opinion on solving this problem.  In the past if the engine were a least started every week there wasn't any problems.  I didn't think that the oil pump could 'lose its' prime".  I was thinking of pulling the 'bladder' tank but we're really stumped. If the pump is bad, how big a job to repair?  The local mechanics aren't really familiar with this engine and I need an 'experts' opinion.


This is a very, very common problem.  The oil pump has lost its prime and the fix should be pretty simple.

On the rear of the accessory case, just below and to the right of the magneto, there is a dome shaped brass plug.  This plug is usually safety wired in place, but it is not unusual to see no safety wire.  If the safety wire is missing, then this tells you that the previous owner or operator probably had to prime the oil pump on occasion.  If the engine is a chronic offender in losing oil pump prime, then the safety wire goes missing as it is too hard to safety on a regular basis.

If the oil pump gears are worn enough to let the oil flow back down into the sump between flights, then the dry gears might not be able to create enough suction to get the oil circulating again. For a quick fix, hold the tail as high as possible for several minutes and enough oil will run from the oil screen cavity to the top of the oil pump to prime it. If this doesn't work then squirt oil into the oil screen area.  There is no set amount of squirts, but anywhere from six to twenty squirts will do the job.  Turn the engine over a few times while squirting oil into the case.  Once again, no set amount of turns, maybe six to twelve.

Start the engine and look for oil pressure.  If oil pressure does not return, repeat the process a couple of times.  If the oil pressure does not return after more than three or four attempts, then dig further into the problem. Chances are that the oil pressure returns on the first try.

As I say, this is a very common problem.  The edge clearances of the Continental oil pump tend to wear, and I have noticed that multi-grade and winter grade oils are a bit more likely to drain past the clearances of the pump.  Once the surface tension between the oil and the pump gear and housing is lost, then the pump loses its prime.

If the problem becomes chronic, then your accessory case may be a candidate for a rebuild.  If you look through my posts, you will see that the accessory case/oil pump for the little Continentals is a chronic problem area.  However, I would not rush to rebuild the accessory case if it is simply losing prime.  If the oil pressure is good, you may just want to live with the problem.  Another solution is to use a single grade oil, and the heaviest viscosity allowable for the seasonal temperatures in your area.  If the daily temp is 50 or above, then use straight grade 50 weight oil if your engine is prone to losing oil pump prime

Harry


Switching an O-200 from Generator to Alternator

Hi Harry, I enjoy reading your webiste and have gained a lot of good information on my Continental O-200.  I have a 1965 Cessna 150E with a generator and am looking at putting the same alternator that comes with a 1966 Cessna 150F. I can use some guidance on the paperwork end of the deal. I will not use an STC, but use the information out of the maintenance manual & the parts book. All of the parts bolt directly on to the engine and no major modifications will be done to the engine. Do you have or know of anyone that has done a 337 that I can see to get the required information? It is basically an alteration to the airframe going from one serial # aircraft to another serial # aircraft?

Your simple question gives me the opportunity to provide two accurate, but somewhat conflicting answers.

Installing the alternator on the O-200 requires no additional approval: Just install the alternator with the correct stack up of parts as listed in the Overhaul and Parts manual for the O-200.  It is just a change from the alternator to generator using the drive gear which is currently used on the generator.  The spec number changes on the engine, but this is for the manufacturer of the engine and does not affect the STC.  The engine Type Certificate approves a laundry list of various accessories and Continental simply assigns a spec to the sum total of the various accessories as installed on the basic O-200 engine.  The spec number just streamlines the ordering process during overhaul to ensure that the engine is configured properly for the airframe.  Continental publishes a product manual which details all of the spec models of the O-200.

Bottom line, though, no additional approval is required, just make a logbook entry in the engine logbook that the generator was removed, an alternator installed in accordance with the parts listed within the appropriate pages from the Overhaul Manual.

Now for the conflict:  The engine will be correct if it is disconnected from the airframe.  The airframe will require a separate approval to install the alternator equipped engine as the voltage regulator needs to be changed along with some minor wiring differences.  Unless there is an alternator conversion specifically listed in the 150E parts manual, a Field Approval via FAA Form 337 will need to be obtained.  This should not be a problem so long as you can provide data to the FAA to document that the 150E has been converted exactly to the 150F configuration.  The key ideas to satisfy with the FAA are that the alternator has the same FORM, FIT and FUNCTION of the generator.  The FFF of the alternator is that it is a FORM of electrical generating device which FITS to the engine exactly like the generator and provides the FUNCTION of 12 volts to energize and charge the electrical system.  The same will apply to the new voltage regulator:  The FORM is the same as the new part is a voltage regulator, FITS in the same place with minor wiring change, and FUNCTIONS to regulate voltage.

However, the FAA has a history of making apparently simple changes very difficult due to the limits of personal decision making imposed by the bureaucracy of the organization.  The key to success is documentation that relieves your inspector or approving administrator of any personal decision making.  Usually, the FAA will not accept previously submitted FAA Form 337 as documentation.  But, the reality is, there is a certain amount of tribal knowledge found within owner's groups which can certainly help to navigate the system. 

If you don't belong to the Cessna Pilots Association, www.cessna.org <http://www.cessna.org/> , I would highly recommend that you join.  The CPA is the single best Cessna group anywhere and has a vast storehouse of knowledge on topics like this.  I guarantee that there are dozens of members who have completed exactly what you are asking and can give you the direct info and save you a lot of hassles.  The $55 for the membership is about the rate for one hour of shop rates and I can guarantee that the information available from this group will save that amount of money many times over.

Harry


More A-65 Starter Conversions

Harry,  I have a Luscombe with a A-65-8 and see that they show a A-65-12. Does the -12 have the provisoins for a starter and can a -8 be converted to a -12?

There is a -12 engine, but the stud spacing on the rear of the crankcase are different than the -8. So, the A-65-12 crankcase and accessory case are different and would require the -8 parts to be replaced making it a pretty expensive conversion.  I have never actually seen an A-65-12 engine so it may have been a concept engine which was approved, but never built.  There is also a -9 engine which was fitted with a starter but no generator, but the cases and starters are very rare.  The problem with rare parts is that they immediately make the engine unreliable because spares are hard to find.

Harry


Excessive Mag Drop in RPM Range

I am a new A&P mechanic working at a small repair station and i am having a bit of a troubleshooting problem. i am working on a 1946 cessna 120 powered by a c-85 with 1068.8 TSOH and unknown total time. this plane was signed off for annual in november and everything was working fine. now the problem i am experiencing is an excessive mag drop, but this only happens between 16 and 1900 rpm, and it is normal on all other rpms, higher and lower. i have ruled out the plugs and the ignition harnesses.i suspect failing magnetos (Bendix SL4N), they are around 400 hours since OH. i hope you can give me a little more insight. both the owner and myself would greatly appreciate it. thanks.

The condition which you describe below sounds like a carb problem.  If there is a fault in the mags, then the mags will typically run bad across the spectrum of rpm, or run poorly at either low or high rpm, not in the mid range.  Also, for both mags to fail in exactly the same way at the same rpm is virtually impossible.

The carb, however, is common to the overall operation of the engine and has a number of air/fuel circuits which engage with different amounts of airflow.  The change of airflow is relative to rpm: the more rpm, the more airflow and vice versa.  If one of the metering holes or metering circuts in the carb is obstructed, then the carb will run poorly in a specific rpm range.  There is a transitional circuit which is placed between idle and cruise rpm, and this circuit tends to work in the 1600-1900 rpm range.

Given that this is a C-85, it probably is equipped with a Stromberg carb.  I have noticed that the Stromberg is prone to developing a flat spot in the 1600 rpm range if the idle mixture is not set correctly.  The idle mixture screw is located at the back of the carb, at the flange where the carb mates up to the induction spider.  Adjust the mixture according to the directions found in the engine manual or carb manual.  Here is a link to manuals for the carb:  http://pj260.com/Manuals/  Click on the NA-S3 tab.

Also, here is a link to a number of technical discussions from the Cessna 120/140 owners group:/

If adjusting the idle mixture does not solve the problem, then the carb needs to be serviced.

Harry


T-Craft Engine Mount in Fly Baby

I have read your posts on the interchangability of these engine mounts. I just want a brief clarification. I have a Taylorcraft L-2 mount which, as I understand it, was for an A65. If I want to use it for a C85 will I need to space the mount away from the firewall with spacers? What if I want to use it with an O-200? Are spacers at the firewall the only mod or does it require any mods at the points the mount attaches to the engine itself?


The A/C series use conical rubber motor mounts and the O-200 uses a combination of rubber doughnuts, cupped washers and rubber tube over the though bolt.  The A/C series mounts sit a bit more rearward than the O-200, so a 1-1/8" spacer is required when the O-200 is used on a A/C series mount. I've attached some pictures of the spacer used on my Cassutt to align the engine correctly with the original thrust line


A C-85-8 0r -12 will use the same mount as an A-65/75.  


Harry

Slowing Down an RV-3 for Light Sport?

You have been kind enough to answer my questions in the past so here are some more. As I said in one of my earlier messages to you I would not mind paying you for your info.
I am building a light sport RV-3. There are others out there trying to do the same. I was thinking of a 0-200 but I think that is too much power and the max speed of 138 miles per hour will be exceeded and I want to build a true, legal and fair light sport.

I am a Porsche mechanic and am do many overhauls. I own a J-3 at the moment which I love.

I was thinking of a C-85. I want a starter. What models would you be looking for? Also where can I find drawings for engine mount position, dimensions, and overall views of the small Continental engines.

There are a few RV-3's flying at this time with 0-200's and I hear that people love them but the word is out that they are too fast for light sport.
If you have any other ideas for engine size I am all ears.

The easiest way to slow down your RV is to install a climb prop with enough length to limit rpm.  The engine horsepower remains available, but you can choke down the cruise by flattening the prop pitch.  The C-85 and O-200 are roughly equivalent in terms of weight to power.  The C-85 has a lower compression ratio and turns fewer rpms to make 85 hp.  An O-200 can be used, just turn it slower.  Extending the wing will slow the plane down and improve the low speed end, but juggling the aerodynamics can upset the balance of a pretty good design.

The most common model is the C-85-12, which is nearly identical to the external O-200 dimensions, except for the motor mount locations on the case. I don’t have any drawings for the actual engine and, so far, Continental has not provided me with any details.  The circular spacing for the four mounts on the engine is the same between the A-65, C-85 and O-200.  The castings for the motor mounts on the O-200 case sit 1 ¼” further forward than the C-85.  If someone in the RV world has installed an O-200, then the basic motor mount info is out there- just shorten by 1 ¼” for the C-85.

Your engine dilemma is the easy part.  Fundamentally, the RV-3 will probably not make LSA approval as the FAA bases the LSA figures on Vans factory specs, and the Van’s factory specs exceed the LSA limitations.  Unless you build an RV-3 and can convince the FAA to license it as something else, the FAA will probably not buy off on an LSA approval.  The FAA has bombarded with methods to defeat the system for LSA approval and it is pretty tough to get around the rules.  So far, the FAA is not accepting aircraft placards to prevent exceeding LSA performance.  The LSA candidate has to physically demonstrate the capability to remain within the performance limits. 

Harry


C-90-8F Starter

Maybe you can help? I am thinking of buying a Piper Vagabond which is fitted with a  Continental  C90-8-F. I want to change the engine to one with starter and a generator. I would use the B& C lightweight units.

I don't have any hassle with the FAA because I am in England and we have a fair latitude with what we can do.

Can you tell me which Engine Dash number I could use that would not need a change to the motor mount, other that perhaps a minor change to allow for clearance of the starter?

The C-90-8F cannot be converted to a starter due to the rear accessory case, engine case and accessory gears are different than engines configured for starters and generators.  So, if you want a starter and generator, the engine must be changed out for another model.  The good thing is that the engine you have is rare and highly sought after by the vintage aircraft mob, so selling it will take a matter of minutes.  The most direct replacement would be a C-90-12, which is even a more rare beast than the C-90-8.  A more easy to obtain engine is the C-85-12, but the horsepower is a bit less and the prop may require a re-pitch of the propeller.  The O-200 can be used, but 1 ¼” spacers will be required to space the engine correctly to the existing motor mount.  

You should probably get involved with the Cub Club or Short Wing Piper organizations as there is surely a number of members who have completed this type of conversion.  I am not sure what type of clearance is needed between the back of the engine and the firewall.  When converting a Luscombe, it is necessary to install a dish in the firewall to clear the added length of the starter and generator.

Harry

C-75 "Downconversion"

I am not a "Flybaby" type, but I would like to ask if there is Continental documentation to convert a C-75 to a C-65. I have a C-75-12 that I would like to use in a Mooney M-18C Mite. The entire STC and conversion process for Mites is very confused and going "Experimental" is not a good option.

I think converting to C-65 and trying to convince the FAA that a C-65 is the same as the A-65 in the Type Certificate could accomplish what i want to do.

There are a number of problems with your plan.  First, there is no such thing as a "C-65" engine, just an A-65.  The A-65-12 and C75-12 are also on different type certificates, which creates a paperwork problem for the FAA. It is much easier for the FAA to consider changes within a single Type Certificate.  The C75-12 and C85-12 are on the same type certificate:

http://www.airweb.faa.gov/regulatory_and_guidance_Library/rgMakeModel.nsf/0/ 73e923a0d5faef7e8525670e004526a4/$FILE/ATTRB7ZS/E-233.pdf

The easiest paperwork path for converting the engine would be to convert the C75-12 to a C85-12.  So long as the correct parts are used in the engine, the data plate can be re-stamped from 75 to 85 with FAA approval. Continental Service Bulletin M47-16, page 11, details the parts changes to convert a C75-12 to C85-12.  Continental Service Bulletin M65-14 provides guidance on re-stamping the engine data plate from one engine model to the next.  However, these two documents provide conflicting guidance for FAA approval, though.  M47-16 specifically states that the FAA needs to approve the data plate change, whereas M65-14 seems to approve simply re-stamping the data plate with no additional FAA approval.  Here are links to these two documents:

http://aeronca.com/ServiceLetters/cont_m47_16.pdf

http://www.aeronca.com/ServiceLetters/Cont_M65_14.pdf


There is an STC to convert the Mooney Mite to a C85-12 which makes installing the engine to the airframe a relatively straightforward process:

http://mooneymite.com/pdfs/STC%20SA3-483.pdf

In any case, you will need to have an A&P participate in the conversion process as, while not complicated, does have a lot of detail.  There is an excellent Mooney Mite owners group and their website can be found at www.mooneymite.com <http://www.mooneymite.com/> .  This group will provide the best guidance for engine changes and will have links to mechanics savvy on the Mooney Mite.

Harry

Follow-Up

I am familiar with both the Mooney Site and the STC you mentioned.  Since A-65-12 engines are very scarce, I want to use the starter and generator capabilities of the C-75-12.

Incorporating the STC makes my problem worse. Converting the C75 to a C85 involves that cost and requires downloading fuel and  restricting max pilot weight to 155# to meet maximum aircraft total weight requirements.

There are several approaches discussed on the Mooney Site, but none has solved the problem of using an A-75 or C-75. What approach does your experience say might be successful with the FAA?

My experience with the FAA is to not expect any assistance to solve the problem you have described.  The FAA is not a risk taking organization so their initial answer is "no" in terms of changing anything in a Type Certificated design.  To give the FAA some leeway, what is the benefit to them to introduce an unknown variable into a solid, certified design?  The Mooney Mite group is going to have much more experience than me in getting engines approved on their airframes, so they will have to guide you along from the airframe side.

Regarding the engine, I can't find any supporting data to de-rate the C75-12 to A-65-12 status.  The C75-12 and A-65-12 engines are subtly different and use different crankcase and cylinder assemblies, hence the different Type Certificates for the two engines.  In short, the FAA will likely focus on the many differences as opposed to the similarities.  So, it is possible to de-rate the engine in theory, but in practice it will be difficult to get approval.

This is not to say that the FAA can't be convinced to make the approval. The FAA will want to see documentation to prove that the engine will actually make 65 hp when de-rated.  There is a copy of a 337 for a one time approval for a C75-12 on the Mooney Mite at the Mite site.  The FAA won't approve your installation based on this approval, but it is a template to develop your own 337.  The point is, you can generate a proposed 337 which uses a lot of the data from the existing 337 and change it to fit the equipment particular to your plane, such as the propeller.

Here is a comment about 337 forms from the Aeronca discussion group by a member who is with the FAA:

(An existing Form 337).constitutes acceptable data that may be considered for a future Field Approval but is NOT a guarantee. The older 337's are approved data for the same make and model, not just the one listed on the 337. They will make your Field Approval much easier to approve and generally will not require coordination with the ACO. All Field Approvals now will need Instructions for Continued Airworthiness included with the application. It's up to the applicant to provide all the data and, as I've said before, having an IA with a good relationship with the FSDO to work all this is essential. No matter what you want to do it probably has been worked and approved somewhere. Joining a type club really pays off because a lot of these early 337's are available. Anyone can order the records for any airplane from the FAA and get the CD with all the airworthiness stuff scanned in. All you need is the N# and Serial #. If you know someone who has what you want ask how he did it and/or order the records.

There's much more to the process but that's the acceptable vs. approved deal.

The point is that the 337 posted at the Mite site is an excellent starting point.  You have to develop a 337 form specifically for your aircraft, and the data may look exactly like the existing 337.  The final point is that you will need an IA to work with the FAA.  It is unlikely that a non-mechanic rated individual is going to get any FAA approval.  I should never say never, but I work with the FAA daily and it will be difficult without a good IA.

I think that getting a one time approval via STC can be done, but it will take some tact and patience while working with the FAA.

Harry

"Just a Little More Power," and a High Fuel Flow Problem

I have an 0-200A with 408hrs SMOH and 208hrs since new superior cylinder kits. This is all in my homebuilt Varieze. I am wanting to get a little more power into the airplane, and am wondering what your thoughts are on 0-200 modification (eg – C-85 or Lycon pistons) over the installation of a 0-235.

I am aware that you can install C85 pistons with some minor machining, or the bolt in Lycon pistons that are available in a range of compression ratios. How far can you take the engine before reliability becomes of concern? What HP would you net from 8:1, 9:1, or 10:1 pistons from Lycon? Is it possible to get 115hp from the 0-200 and have it reliable and still keep the TBO as standard? My compression readings are all 79/80 currently.

I also have a strange problem that an A&P could not rectify. At mid RPM, there is an ever so slight stumble, more noticeable when reducing RPM than increasing RPM. It never feels like the engine is going to quit or anything, its just noticeable. It just runs rough at a certain point. Either side of that point is fine.

The engine performs like a dream, static rpm is good and top rpm in flight is good too.

However, I find it using excessive amounts of fuel, almost the same – if not more, than a 0-235. It is not my operating methods that are causing the high fuel consumption, in case you are wondering! I flew for approx 3hrs and used near 80 liters of fuel – which is about 26 to 27 liters per hour. That was at 2500rpm, 10,000ft and leaned back. I do not know what is happening there, maybe its standard, I don’t know. It has the MA-3 carb.

Airplane owners who say that they want just “a little bit more power” is just like an alcoholic who says he wants “just a sip”.  A little is never enough…  I think that your question more accurately distills down to the economics of improving the performance of the O-200 vs a complete conversion to a Lycoming 0-235.

From the viewpoint of economics and mechanical simplicity, the O-200 with some improvements and changes in operation will be much less expensive than a conversion to an
O-235.  However, the O-235 will win the horsepower and torque war simply because it has more cubic inches and displacement always wins that battle. A modified O-200 will not make the same horsepower and torque as an O-235.

Increasing the compression ratio and running at a higher rpm will improve the power output of the O-200.  How much?  Who knows!  Unless the modified O-200 is run on the same calibrated dyno as the stock O-200, there will never be an apples to apples comparison.  Most theoretical calculations will yield a number of about 108-112 hp, but no one really knows for sure (especially those who claim that the O-200 will  make 180 hp- no way!). 

Increasing the rpm could be the easiest trick as spinning the prop faster simply gives the engine more opportunities to turn hp into thrust over a given period of time.  At 2500 rpm, horsepower is turned into thrust 2500 times each minute, and at 3200 rpm there are 3200 opportunities to turn horsepower into thrust.  However, physics being what they are, the friction of turning more revs will theoretically reduce the TBO.  Higher revs will increase the wear to cylinders and bearings over a given period of time.  An engine turning 2400 rpms over 1800 hours will wear at a slower rate than an engine turning an average of 3200 rpm over 1800 hours.  The higher rpm also requires that the engine and prop be more finely balanced as the effect of vibrations increases as the frequency is increased due to an increase in rpm.

Increasing the compression ratio helps the engine to develop the torque to push a more coarsely pitched prop.  A negative to high compression pistons is that you can’t run mogas.  Higher compression also develops more thrust stress and wears bearings faster.  The C-85 pistons can be modified to provide adequate clearance with a ¼” wide, 45 degree chamfer at the perimeter of the piston crown.  The LyCon pistons are more aggressive with the compression ratio, and the more popular choices fall between 9 to 10 to one.

Your midrange rpm problem is probably related to your high fuel flow. Usually, high fuel flow occurs when the carb accelerator pump starts to leak, allowing more fuel than required to run the engine to be pulled into the intake.  A leaking primer will also cause this problem.  The carb probably just goes overly rich due to the leaking accelerator pump and the engine stumbles.  Another consideration is that you may not  have the correct carb installed.  The MA3 is a family of carbs with a range of part numbers specific to particular engines.  The part number for the O-200 carb is 10-4894. 

Another problem chronic to stock O-200 carbs is the change from the multi-piece to one piece venturi.  If a one piece venturi is installed in the O-200 carb, a “pepperbox” fuel discharge nozzle needs to be installed. If the stock nozzle is installed with the new one piece venturi, then the engine will run overly rich.  The pepperbox nozzle helps to atomize the fuel better.  Precision used to have a good troubleshooting page at their website, but they have recently sold the carb line, so that info is no longer posted.

Harry

Plug Recommendations, and Other Rebuild Parts

I'm gathering the last bits and pieces together for assembly of my Fly Baby motor and I have some questions.

I'm buying a shielded harness probably from Fresno. Apparently I have a choice of plugs. Any specific recomendation?

Is there any cheaper source for conn rod nuts and bolts then Fresno?

Should I get a NEW oil press relief plunger and spring?  I have 2 springs, one is 3.5 inches and the other 3.75 inches.  Both the same color-dirty black.  I know the oil section is touchy and I want to do it right.  Pump was totally rebuilt by Central Cylinder.

Should I re-use the crankshaft key or get a new one?

In my manual, there is a snap ring shown on top of the socket in the tappet body (page 53 figure 38 index # 6)  It's listed as part number 530940. Until noticing this I didn't think there was suppose to be a snap ring in this location. Weren't any when I took it all apart.  My manual is TCM revised Nov 71

Fresno is probably the least expensive source for A-65 parts.  You can shop around and maybe save a buck or two, but you will burn up a lot of time, also.  The conn rod bolts are simply expensive, no matter where they are purchased.

The 5/8-24 spark plugs are the most common for the A-65.  The Autolite UREM40E are the least expensive and the best deals are through Aircraft Spruce.

Regarding parts replacement, you are venturing into "do as I say, not do as I do" territory.  I advocate installing as many new parts as possible.  I will recycle parts only in pinch to fix a problem quickly or on engines for my personal use.  I am willing and able to support the problems of using recycled parts.

I'm spending your money, but after you have invested a lot of money into a crank, cylinders and new bearings, I probably wouldn't get cheap with small pieces.  The A-65 suffers chronic oil pressure problems, so I would not hesitate to install a new oil pressure spring.  I install a new plunger, spring and face the seating surface in the accessory case where the plunger mates up.  I don't know what the crankshaft key costs, but that is a pretty critical part, so I wouldn't skimp on that, either.

The tappet bodies vary, and the ones used in the A-65 usually don't have the groove for the snap ring.  The snap ring tappets are usually seen in the C-85 on up.  But, due to parts changes and migration from one engine series to the next, it is possible to have the snap ring groove.  If the groove is visible, install the snap ring.  If not, don't worry about it.  The snap ring really only serves to hold the pushrod socket cup in place when the pushrod and rocker arms are not providing pressure to keep the socket seated.  Problems do occur when the cylinders are pulled as the little cup falls out of the tappet body, gets wedged between the pushrod housing and the top of the tappet body.  If this problem isn't caught before the engine is turned over or started, then everything binds up and the pushrod bends, the housing cracks and the tappet caves in the top of the tappet body, which then becomes a major repair to remove the tappet body from the case.  Don't ask me why I know about this problem.  The point is, be careful to make sure that the socket cups are seated correctly if there are no snap rings installed.

It sounds like you are slowly but surely getting your engine together.  Feel free to drop me a line anytime.

Harry

Timing the Slick 4001 and 4003 Mags

I am getting very close to finishing my Fly Baby and I have a question regarding timing the 4001 & 4003 Slick Magnetos that I am trying to resolve. I have seen your article in AMT on magneto timing and I have also read the Slick Aircraft Product information sheets by Unison Industries. I feel between these 2 articles I can get this done.  I have the old throw away series of magnetos and apparently these are the impulse coupling type so I will not be able use a T-123 timing pin? Nor will I be able to use the T-150 E gap tool? If neither of these tools will work how does the internal timing of the older magnetos get verified? I currently have neither of these tools but for < $20 they can be had. These older magnetos came from my Godfather who honey holed these for a specific project MANY years ago and he swears these are good to go. I of course want to verify internal timing before I install them on my Baby so any help would be great.

The 4000 series are a bit different than the 4200/4300 series magnetos, so the timing procedures and tools required are a bit different.

There is a vent plug on the bottom of the magneto which can be removed to expose the rotor shaft.  If you turn the rotor shaft, you will see a small dimple or drilled hole.  The magneto must be "sparked out" to find the position where the distributor is postioned to fire cylinder number 1. Cylinder #1 on the Slick magneto is in the 2 o'clock postion with the capacitor of the magneto oriented horizontally in the six o'clock quadrant of the magneto.  Insert a paper clip into the cylinder #1 tower so that a spark can jump to the frame.  Snap the impulse coupling through until a spark occurs.  Turn the rotor shaft backwards until the dimple in the rotor shaft appears in the vent plug hole.  Insert a small finishing nail into the dimple to hold the magneto rotor shaft in the firing position and install on the engine.  Be sure to set the engine up to position the crankshaft to the firing positon for cylinder #1.  The good thing about the 4000 series is that no special tools are required.

By design, the 4000 series was non-repairable and no spare parts or tools were ever sold to repair that series.  So, there really is no service which can be accomplished to the internals of the magneto.

However, a bigger issue is that you  have two magnetos which are not compatible to be run together.  The 4001 is a Left Hand rotation magneto and the 4003 is a Right Hand rotation magneto.  The Continental engines require that both magnetos turn the same direction.  The A-65-8, or any Continental designated with a -8 in the model number, requires Right Hand rotation magnetos.  The 4003 would be correct for this engine.  Continental engines designated by -12, -14, -16 or the O-200 series all use Left Hand rotation magnetos.  In this case, the 4001 magneto would be correct.

The next question will be whether the rotation can be reversed and the answer is no.  The rotor shafts are specific to rotation and the magneto will not produce any spark energy when turned backwards.

So, at the very least, you will have to find one replacement magneto.  More bad news is that Slick does not acdcept the 4000 series for core value any longer, so you will hve to pay extra for the ne 4300 series replacement. The magneto for the -8 series is the K4335.  This magneto/gear combo and includes a drive gear specific to the 4333 magneto ( the gear from the 4003 will not fit the new 4333).  The replacement for the 4001 magneto is the 4301 and your existing drive gear will fit this magneto.

Sorry about the kind of bad news, but better to be forewarned than disappointed when you are ready to run the engine.

Harry


Slick Mag Wiring

I will be replacing the Bendix magnetos on my C-65, with Slick 4333 magnetos.  The problem is, I don't have a wiring diagram for the Slick mags. I haven't had any success in finding a wiring diagram on the internet.  Can you help?

My airplane is a Pober Pixie, that I completed in 1985.

The firing order for your engine is 1324, and the #1 cylinder for a Slick magneto is in the 2 o'clock positon and turns clockwise from that position. The left magneto fires the top plugs and the right fires the bottom plugs. The spark plug nuts on the Slick ignition harness are marked for their respective location, T4 for top #4 plug, B3 for bottom #3 plug and so on.

If you are ordering the 4333 magnetos alone, they won't fit without the special gear which fits the magneto.  To get the mag and gear combo, buy the K4335.  This is a 4333 and gear.  However, check the price of two K4335 to the complete Slick kit of K4334.  The K4334 includes the mags, gears, harness, plugs gaskets, everything for install.

Harry

Starter Replacement for an A-65-9

I have one on an Aeronca 11CA that was overhauled in 2000 by Gann Aviation Lafayette GA. It has a total of Four Hours since rebuild, Why? you ask.  Well I can't find a Starter.  I took the back plate off and looked inside and it has a Bendix type Engagement rather than Gears.

We put Two New Slick Mag's, but they do no make one with Impulse Couplings.

What do I do now? Any suggestions of where I might find an Eclipse Starter that fits the -9?

I have only seen a couple of these starters and I have never really looked at the details of the installation.  They are really heavy though, maybe 8- 12 lbs or so.  If you do find one, I would think that it would be relatively easy to fix.  You might want to contact Sky Tec starters at SkyTecAir.com and see if they could match up a starter to the -9.  They will probably say that they don't make anything, but maybe if you send some pictures and dimensions they can match up something.  Other than that, start scrounging Trade-A-Plane and all of the Cub, Aeronca, Mooney Mite sites to see if a starter can be found- I'm sure that someone has one scrounged away.   No easy answer for how to find a starter.

Because the -9 accessory case has a different accessory case than all other Continentals, the depth of engagement of the magnetos is also different. The big problem is that there is no magneto drive gear combination for the impulse Slick magneto which gives the correct depth of engagement.  The 4302 is the only Slick magneto approved for this engine.  I worked for Slick for 20 years, so if there was a solution, I would have found one.

One roundabout way to solve the problem is to convert the -9 to a -8.  You lose the starter, but you gain the ability to install impulse mags, which significantly improves the hand propping performance.

Harry

Reducing the Fuel Burn

Flying a jodel with a o200 in it the price of petrol in Australia is getting prohibitive  what can i do to increace efficency? Has EFI,  Electronic ignition been used with any real  effect? I fly under R A A and can do modifications.

I don't think that there is much you can do to reduce the fuel burn with any noticeable effect.  Check out www.lightspeedengineering for an ignition. Klaus Savier has had good success with efficiency, but his airplane is very specialized and his benefits were not achieved via the ignition alone.  You may be able to save a bit of fuel, but the cost of the ignition system will probably cost more than the fuel savings you would realize over many years of flying.

Harry

Continental C-90 Oil Strainer

I have a C90-12f engine now installed in in my J3 cub, it replaced an 8F version which was worn out.

The 12F is deeper at the back end and the oil strainer casing conflicts with the cub exhaust /heat muffler. I have installed the spin on oil filter conversion on the side of the engine and change the filter every 25 hrs. My question is: could I remove the strainer housing completely and blank off the port to gain extra space behind the engine ? or are there any potential pitfalls to this action?

If you read the details of the STC, one of the details of the installation is to remove the strainer screen.  However, I think that the direction is to remove the screen element, but retain the brass housing for the screen.  As far as completely removing the housing, I am not aware of any specific approvals or parts to change the screen housing to a different configuration.  Almost certainly, the FAA would want some sort of approval to change the housing.  The oil temp probe is also installed into the screen housing, so you would have to figure out how to adapt that, also.  To get the correct placement for temp pickup you would need a housing the same depth as the stock part, so I'm not sure what you can gain by removing the stock part.

Harry

Break-In

I have thoroughly enjoyed reading your vast amt of wisdom on the webpage - thanks for sharing so much!

I have bought an A-75-8 engine that was overhauled in northern Calif 33 years ago and never run; just stored with humidity plugs and quite a bit of internal grease (borescope). It was pretty thoroughly gone through, with new camshaft, lifters, valves, guides, pistons, rings, etc. Cylinders were chromed, which is probably good, considering the down time.
I have installed it in my '48 Piper Vagabond PA-15.

My questions are:

1) how to prep it for that first start?
2) How to break it in (ground run and first few hours, with those chrome cyls)?

Many thanks!!

Here is a link to the Continental Service Bulletin regarding engine operation during break-in:  http://www.tcmlink.com/pdf2/M89-7R1.pdf.  Also, here is Lycoming's recommendations for engine break-in: http://lycoming.textron.com/support/publications/service-instructions/pdfs/S I1427B.pdf   Between these two documents, there is plenty of guidance to properly break in just about any engine.

The prep detailed in the Continental Bulletin before running is a bit non-specific, and basically suggests turning the engine over a number of times to ensure that spark occurs, and the engine is not binding up.  I usually remove the top and bottom plugs, disconnect the fuel flow to the carb and turn the engine over about 100 times to get some sort of oil flow through the engine.  You won't see any oil pressure while turning, so don't worry about that.   Turning off the fuel flow is very important as fuel can be pulled into the cylinder while cranking.  Excess fuel can wash the oil off of the cylinder walls and scoring can occur.  Don't over think the pre-oiling aspect.  There are all sorts of pre-oilers on the market, but these are really overkill for the little Continental.  Pre-oiling is a legitimate concern for big bore turbocharged engines due to long oil pressure paths, but not so much for the four cylinder Continental.  Turn the engine over a few times to make sure it is free and that is really all you need to do.

M89-7R1 also details ground run procedures.  Start the engine, establish oil pressure, and run it for five minutes or so to make sure it generally runs. Shut it down, check for leaks, re-start.  It should only take about 20 minutes of off and on ground running to get the idle set and determine if the engine will be ok for flight.  DON'T RUN THE ENGINE ON THE GROUND AN EXCESSIVE AMOUNT!!!    NEVER ATTEMPT TO BREAK-IN AN ENGINE ON THE GROUND!! Excessive ground runs will certainly glaze the cylinders, resulting in a polished surface which will not hold oil or compression.  Break the engine in under load, in the air so that adequate cooling airflow is available.

Once you get airborne, don't baby the engine, run it at 75% or more for the first five hours or so to get the rings to seat.  During flight, run at 75%-100% power for the first hour, and then vary the engine output from 100% to 65% and points in between every 30 minutes for the first five hours to ensure that the rings seat properly.  One of the biggest mistakes is to baby an engine during break in.  The problem is, not enough friction is developed when babying the engine, so run it aggressively- if that term can be applied to an A-75!

Regarding oil, opinions are all over the place on this topic.  Generally, there are two camps:  break-in on non-detergent oil or break the engine in using what the engine will run during normal operation.  My observation is that since there is no clear evidence to support that one type of oil over another is clearly superior, then all types of oil must be relatively equivalent.  What is clearly important, though, is the mechanics of how the engine is broken in, namely running the engine aggressively as discussed above.  I do tend to avoid oils with anti-scuff additives and run straight oils in the engine.  You can never go wrong going the traditional route of non-detergent straight weight for the break in, and then switch to the oil which will be used for normal operation.

Other than that, the aside from gaskets, the age of the engine overhaul may or may not be a factor.  I would just run it and see how things work.  The biggest problem will probably be gaskets which have just aged and may leak.

Nice looking Vagabond!  Let me know how things work out.

Harry

A-65 in a Zenith CH-701

I am building  Zenith CH 701. In your opinion is this the 65 a good engine for this airplane? Will it turn a 72 inch prop? What is the weight of a 65?

I have had contact with a few builders have have either used or are planning to use the A-65 in the Zenith 701, so it must be feasible.  I am only generally familiar with this airframe, so I can't answer the question with authority, however.

The weight of the stock A-65 is listed as 170 lbs dry.  Installing Slick magnetos instead of the Bendix SF4 series will shave 6-8 lbs off of the engine, but there are not many other things which you can do to save weight. Most of the stock prop diameters for Cubs, Champs, Mooney Mites and so on will use a prop diameter of 69-76 inches.  A 72" prop should not be a problem, but I don't know what the pitch will be.  For equal performance, a smaller diameter prop will have more pitch than a larger diameter prop.

Harry

Oil Filters on A-65s

What about oil filders on A-65?  I've heard bad things.

In summary, the cons are perceived to be the extra weigth and the low output of a worn A-65 oil pump may not be able to overcome the fluid drag of the oil filter. These are valid comments, but don't really condemn the oil filter as a problem.  Certainly, the A-65 will chug along for years without an oil filter.  However, had suitable oil filters been available when the A-65 was originally designed, it is certain that a filter would have been fitted. The A-65 uses a screen because that was the standard filtration for engines in the 30's.

All modern manufacture engines use filters, so the weight of numbers in the current sense is that a filter is more effective than a screen.  Lycoming engines, in fact, double the oil change time from 25 hours for screen engines to 50 hours for filter engines.  So, filters must do something right.

The filter will not cause the Continental engine pump to fail.  The pump fails pumping due to out of tolerance wear, not hard work.  So, if the pump is making normal oil pressure in a worn state, installing a filter system which requires a bit more pumping action due to the drag of the filter may cause the oil pressure to drop, as the worn pump cannot overcome the added drag.

As I stated before, I have run oil filters on the little Continentals and run the same engines with no oil filters.  The filters definitely catch bits of debris, but I don't really have any proof that the filter will extend the life of the engine.  Common sense clearly dictates that a filter is better at filtering contaminants than a screen. 

I tend to prefer to keep my engines light and simple, so I usually don't worry about a filter on the A-65.  I keep one installed on the O-200 in my Cessna 150, but this airplane sees a lot of flying, so it saves time to change the oil every 50 hours, simply out of convenience.  I would have to change the oil every month instead of every couple of months or so if I didn't have the filter.

So, my perspective is that there is no right or wrong to using a filter.  It largely boils down to convenience of reducing oil changes and providing just that extra bit of filtration for the pampered engine.

Harry

A-65-12 Cases

I recently purchased a 1941 J3-C65. I want to build a C85-12 engine and I have purchased a used case. I have spoken with Aircraft specialties in Tulsa about purchasing the STC and the 0200 crank and rods and plan on proceeding with this mod. My question is about the accessory case. The case I purchased did not come with one. I am curious about what options are available. I have a friend with a collection of C65 and 0200 parts but no C85 parts. What accessory cases are interchangeable with this configuration and are there any issues I should be aware of.

This is a pretty simple answer.  The crankcase will be specific to either -8 or -12 configuration.  As such, only a -12 or O-200 accessory case will fit a -12 accessory case.  There is an STC to convert the -12 to-8 status, but it is an expensive proposition and I can see no benefit.  The new O-200 accessory case is a much more durable set up and is an approved replacement for the original -12 accessory case.

Edgcumbe G&N usually has the best prices for the accessory case and oil pump gears, 800-621-1319.  I think that a case is about $800 and the oil pump gear set is about $350.  Old rebuilt -12 accessory cases are just a couple of hundred bucks less than new.

Harry

How Can You Tell a Chrome Cylinder?

How do you tell if cylinders are chrome or steel? My cylinders don't have the orange band around them and they don't seem to have the little chicken feet cracks in them. I ordered rings for steel cylinders, but hate to find out the hard way that they were chrome.

This is where a trained eye is handy.  The orange band is the most visible identifier, and the shiny surface with micro-cracks is the next best way. The chrome surface is unique looking, but if you are in doubt, I would recommend an experienced second set of eyes take a look.  In this case, there is no other shortcut than experience.

Harry

On Carb Ice

Hi, I have recently bought a 150 g It has 570 hrs on it since the rebuild in 1980. I soloed in 1-08 and need to know about the proper use of carb heat. I have 20 hrs solo time and last week I noticed the engine running a bit rough and I think it is because I have been over using the carb heat. The mags were dropping about 80-100 the mechanic told me to do a runup and lean it out for a minute or so and it cleaned it up some. But I flew today and the engine just doesn't feel like it is running to its peak. I live in Wisconsin, today it was about 40 out I was up at 3,500 ft I noticed the rps dropping so I pulled the heat and the engine ran rougher than heck for 15 sec when I pushed it in it ran ruff for a couple secs and then cleared up. Is that icing? In all the reading I have done it seems carb ice and improper use of the carb heat is the culprit for engine problems. I need to learn more on carb heat and mixture control so I feel more in control when I'm flying. I use 100 av gas. So any words of advice would be very welcome and if there is any books that you know of that might help me understand.

Carb ice is a relatively sporadic event, and takes a fair amount of humidity with a fairly tight temperature and dewpoint range.  Theoretically, carb ice can occur at any temperature, but the reality is that carb ice is much more likely to occur when there are large amounts of moisture in the air.    The only accurate way to detect carb ice is via a carburetor temperature probe which can measure the temperature at the venturi.  The temperature differential of the airflow will be the coldest at the venturi and ice occurs in this location.  If the temp hits 32, and there is moisture, ice is likely to occur.  However, for the most part, carb ice cannot be induced or experienced at will or during most atmospheric conditions.  Carb ice usually occurs when the velocity of the airflow through the induction is reduced, which causes a temperature drop between the intake and outlet of the carb venturi.  So, carb ice is more likely to occur when the throttle is reduced than at cruise rpm.  In fact, is nearly impossible to experience carb ice while at cruise rpm.  Not impossible, but very unlikely.  I have experienced carb ice once at cruise and the conditions were clearly evident that ice was likely.  The weather was marginal VFR, lots of moisture with low ceiling and low visibility, and an outside temp of 34 degree.  The weather conditions were not subtle.  If the temp is 40 degrees and good VFR, it is not likely that you would experience carb ice.

The use of carb heat to prevent or clear carb ice is simple:  Full on or full off.  If carb ice is suspected, then carb heat is applied fully.  In the worst circumstance, the engine may run roughly for a moment, but once the ice is cleared the engine should run normally.  Once carb heat is off, the engine will gain a couple of hundred rpm and run smoothly.  Carb heat will not make the engine run rough in either the on or off condition.  You cannot "overuse" carb heat.  Carb heat will make the engine run slightly rich as the warm air expands which results in a ratio of more fuel molecules to air molecules.  So long as the engine is in good mechanical repair, the slight richness caused by the carb heat should not be an issue. Conceivably, if carb heat were left on 100% of the time, then the plugs may load up with carbon.  However, the engine should be able to support having the carb heat applied on downwind and left on until touchdown.  However, engines vary and what works for one engine, may not be the same technique for another engine.

I would recommend that you have your mechanic or flight instructor fly with you so that you can demonstrate the problem to him.  He may have some additional thoughts if he experiences the condition firsthand.

Harry

Rough Engine - Cutting out on Takeoff

I have a C-140 C-85 - 12 and NOBODY can fix it! Seems unbelievable, but true. Problem started with rough engine at Annual time. (But flyable)  After 3000.00 dollars in new magneto's, new drive gears, harness, plugs, and carbureator overhaul THREE times (D&G, Niles MI.)  Not too happy with D&G!!!! NOW, I have an airplane that tried to quit on me three times with attempted takeoff's. Got 100 feet in the air one time. GREAT. Now I have an airplane that I don't know what to do with. Maybe part out. (And it started out as a top notch C-140.) The Continental has 500 hours since major to new specs. ECI cylinders, new cam, and lifters, etc. Fuel is 100% fresh as well. Compression great on all cylinders. Valve action checked under each valve cover. Timing perfect as well. NO ignition issues.  I guess that the C-85 Continental is too complicated for anybody, in 8 weeks of fooling with it, to figure it out. So much for certified folks. The engine looks nice, just hanging there.  I see the web info on Experimental hotrod tips on the little Continentals, etc, and I find that hard to believe. Heck, they can't even get a stock engine to run right.  How do they do the super stuff? Indiana sure doesn't seem to possess any of these super mechanics. 

Specifically, It does not really run good throughout RPM range. half way acceptable mag check. Static 2250+ . On takeoff, tail up, then BOG, lose RPM, like you pulled the throttle. That didn't happen before the work.

Carbureator was supposed 100% overhauled and yellow tagged. New steel needle and seat. Supposed replace A65 venturi and A65 main jet with proper C-85 venturi and jet. Who knows.  With old needle and seat carb did not seep. Now it wets carb airbox over a couple of hours sitting. Thats what 300.00 and a yellow tag will get you. The automotive carb shop here in indpls can do better than that!   (Also, new intake runner "doughnuts installed)

Harry, What do I do with it! I can't even fly the thing, with its wonderful Continental to the junkyard. I am about out of money to dump on it, just to go backwards some more. Maybe just a little more money to the "Certified Mechanics" will get me to the seen of the crash first!!  I have attempted to go thru proper channels / procedures to get it properly repaired, and this is what I get.  After 30 years, I have never seen anything like this.

HELP!!!

It really sounds like you are having a tough time with this engine!

First, let me offer some troubleshooting psychology.  You are obviously worked up and frustrated over this situation, and the emotional reaction to this problem will inevitably prolong your troubleshooting efforts.  The engine is a mechanical device governed by rules, not emotion. Troubleshooting is a logical, step by step process which requires a clear thinking and an unemotional, methodical approach.  Your engine is just a machine, governed by rules, so it can be fixed.

First, I would highly recommend that  you join the Cessna 120/140 organization (if you don't already belong).  If you own a Cessna 140, it only makes sense to seek the assistance from other owners of an airplane exactly like yours.  Because their focus is on a very specific range of topics, it is certain that someone in that group can guide you along to fixing your problem.  I guarantee that if you sold your airplane to one of the guys in the group for $1000 it would be running perfectly in short order!  Check out http://www.cessna120-140.org/forum/index.php to access the tech topic discussion list.  You don't have to be a member to read the postings, but you do have to be a member to make a post.  I have been associated with the 120-140 group for many years, and my opinion is that it is one of the best owner groups out there.

Okay, let's move on to the troubleshooting.  If I were standing in front of your plane, I would literally start from scratch.  The first thing I would check is the overall compression.  A simple pull through of the prop would probably be sufficient at this point just to get a feel for the compression and if the cylinder can hold compression for a few moments with the piston at TDC.  Any major compression problem or valve problem would be detected. An engine will run with a minor valve or compression problem, so, at least at this point, I wouldn't be concerned about doing a detailed compression check.

Next, I'd inspect the spark plugs.  The appearance of the electrodes should be uniform in color, somewhat brownish in tint.  If all of the plugs look blackish or are sooty, then the engine is running too rich, perhaps due to a leaking primer or overly rich carb.  If the plugs have no color, then the induction charge is too lean, perhaps due to an induction leak.  If just one plug is a noticeably different color than the others, then there is likely a valve or induction problem.

Moving on, I'd take off the valve covers to check valve operation.  I'd look for excessive valve lash, or the clearance between the pushrod and the rocker arm.  When the hydraulic units in the valve train are pumped up, the pushrods should have little to no fore and aft movement.  If one of the pushrods is noticeably looser than the others, this could be an indicator of a collapsed hydraulic lifter.  I'd also check to see if the valves are opening and closing and look for any indications that a valve may be sticking.

Next step would be the intake tubes and make sure that they are centered and tight.  I have seen times when an intake tube is not inserted fully into the rubber coupling.  So, I would loosen the couplings, and slide the intake tube back and forth to make sure that each end is captured by the couplings. Also wiggle the intake elbows to check for any looseness.

The inlet filter to the carb airbox is next, check to make sure it is not blocked.  With the filter off, check the operation of the carb heat flapper valve.  The flapper should be tight on the shaft and should travel fully up and down when the carb heat selector is moved.  Using a mirror, check to see that the butterfly valve in the carb moves from fully closed to fully open when the throttle is moved.  External to the carb, check to make sure that the operation of the throttle arms is free and that the cables aren't dragging.

Time for the magnetos.  It is possible to install the magnetos incorrectly and still have the timing light indicate that the contact points are opening at the correct firing point.  When the magnetos are installed, a timing pin is inserted into a hole in the distributor block to align the distributor finger to fire on cylinder #1.  In the case of the 4301, both magnetos are pinned for "L" or left rotation.  A common mistake is the pin the right magneto for "R" because it is on the right side of the engine.  It only takes a few minutes to physically remove the magnetos and re-time them to the engine.  I have found time and time again where mags are mistimed to the engine, and the only way to catch this is to re-time the magnetos to the engine.

Another thing to check is the ignition wiring harness.  The firing order for the C-85 is 1-3-2-4.  So, looking at the harness cap where the wires come out, you will find a number "1" cast into the cap.  Moving in a counterclockwise direction from tower #1, the next lead should run to cylinder #3, and so on.  Also, make sure that the leads on the top left side of the engine are not reversed.  The #4 cylinder is the forward cylinder and the #2 is the rear cylinder.  The #2 cast into the case to denote this cylinder sits a bit behind the baffling, and the #4 sits closer to the #2 cylinder, so it is easy to reverse the two leads.

At this point, if spark, fuel and the timing of matching the two together are confirmed, your engine should start.  It sounds like starting has not been a problem, so at least we know that the engine starts.  Do a static engine run and just check the mags at a variety of rpms.  The engine should run the same on both mags.  If the engine runs significantly better on one mag vs the other, then there is an issue with the magneto or magneto timing. If the engine runs ok, or poorly in the same way, on either magneto, then the carb is suspect.

If the troubleshooting points to the carb, there is not much else to do than to install a different carb or send the suspect carb to a shop for bench testing.  If you feel that the shop you have been using is not working out, then try another shop.  I use Aircraft Systems in Rockford, IL, 815-399-0225.  This shop is extremely reliable and very analytical and will know if the carb, at least on the bench, is in working condition.  Another option is to find or borrow a similar carb to see if another carb changes the engine operating condition.  Swapping the carb for another carb would be my preferred approach.  If the engine runs poorly on the second carb, then the problem is something else.

My strongest recommendation towards solving your problem is to contact other Cessna 140 owners via the 120/140 owners group.  There is a lot of "tribal knowledge" to be found there, so take advantage of their resources.

Ultimately, don't try to fly your airplane if the problem is detected during a run up or during test acceleration down the runway.  Engine operating problems do not improve once the airplane is airborne and such flights with a sick engine often end badly.  At this point, you, as the pilot, should know better than to try to force a reluctant airplane airborne.  You can't blame your mechanic or overhaul shop for you making the decision to fly a troubled airplane.  Take a step back and stick to a systematic approach to troubleshooting.

Feel free to keep in contact and let me know how your problem progresses.

Harry

One Cylinder Running Hot

I am having a unique problem w/ my C-85.  It has the O-200 crankshaft STC.  #2 cylinder runs hot ( it will go past 450f +, if I let it).  I have changed the intake system (3 times), compared the baffling with 2 other Cessna 140's, changed thermocouple probes several times, and found that by shutting the left mag off, the temp will drop to 'normal' of +/- 325f.  I have swapped cylinder #4 and #2 cylinders and have swapped mags left to right, and changed the left harness, and the problem stays with #2 cylinder position. 


Kind of a puzzling problem with good and bad elements attached to it.  The good is that the problem is consistent to cylinder #2, the bad is that the problem defies logic to a certain extent.  Some of what I am about to explain is basic and probably ground you have covered already, but problems like this are usually rooted in the basics.

Cylinder Photo
I have attached a picture of the position of cylinder #4 and #2.  If you note, the number "4" cast into the case sits closer to the rear cylinder, which is cylinder #2.  The cast number for cylinder #2 is positioned just aft of the baffling.  The point is that cylinder #4 is the forward cylinder and #2 is the aft cylinder and it is very common for the ignition leads to get swapped fore and aft.  The firing order for the engine is 1-3-2-4.  When looking at the face of the Slick wiring harness where the wires come out, there should be a number "1" cast into the cap to denote the lead which runs to the #1 cylinder.  Moving counterclockwise, or left rotation, the next lead should run to the #3 cylinder and so on.  Make sure that the wires leave the cap in the correct order and are connected to the correct cylinder.

Next, both magnetos should be timed for LEFT rotation.  When the timing pin is inserted into the distributor block to lock the distributor gear in a position to fire #1 cylinder, the pin should be inserted into the hole marked "L" for both magnetos.  If the Right position mag was pinned for "R" then this is incorrect.  Do not rely upon what the magneto timing light indicates without physically checking the position of the distributor gear in relation to the timing of the magneto to the engine.  The distributor gear can be positioned to the wrong cylinder, yet the timing light will indicate that the contact points are opening at the correct firing position. The opening of the contact points and the position of the distributor finger are two completely separate things.

If the timing is correct, and the ignition harness wiring is correct, then it is fair to consider that the cylinder may be running lean.  An induction leak will cause this problem, or a crack in the induction port of the cylinder.  When the cylinder was assembled onto the engine, were the correct rings installed?  Chrome rings in chrome barrel will result in very high friction and very high temps.

One final thought is that the pickup for the CHT may be a problem.  The spark plug types of CHT are sensitive to airflow, so maybe #2 is getting a bit different airflow.  Have you swapped the CHT leads from #2 to a different cylinder?  You probably have, but just a thought.  Also, spark plug type CHT pickups will read 25-40F different than bayonet type leads, so if you have mixed the types, then perhaps this is the problem.

Otherwise, shutting the left mag down changes the temperature, it may not be the mag, it may be the mixture in the cylinder.  If the fuel/air charge is too lean, shutting the mag off enrichens the mixture slightly as it will burn at a slower rate.  The slower burn would result in slightly lower temps.

If I didn't know any better, I would bet that the ignition leads are not positioned right to cylinder #2.

Harry

Leaking Oil from a Hole in the Sump

I am looking for advice / help on a 0-300 Continental. It has developed an oil hole in the front of the sump near the frt drain plug.

I suppose I could enlarge the hole tap it put a small bolt in it , lockwire it and then epoxy the whole area. Am I nuts and do I have to change the whole pan?

In that case, can I cut the rear gasket (were the mag/oil pump drives cover is)  right were it meets the sump. Then put a 1/4 gasket on the rear of the sump and bolt it all back on?

This is a very common problem with the C125/C145/O-300 series of engines. The sump is made of magnesium, and there is a cavity around the sump plug internal to the sump where old oil and contaminants tend to collect.  Over a period of 40-50 years, the acidic and metallic content of the trapped sludge reacts with the magnesium, resulting in corrosion.  For lack of a better term, the boss for the oil sump plug "rots" out.  Because the rot is so common, serviceable sumps are hard or expensive to find. 

The approved repair is to remove the sump and send it to Drake Air in Tulsa, http://www.drakeair.com/.  Drake is one of the few, if only companies, to successfully repair magnesium components.  There are probably a number of ways to improvise a non-approved repair, but I have find that the most long lasting results will come the hard way by sending it off to Drake for repair.

If you want to find a repaired sump, the sump has two varieties:  a 3 hole sump and a five hole sump.  The 3 and 5 refer to the number of bolt holes visible at the bottom, left and right side of the sump where it attaches to the accessory housing.  The 3 hole sump will have 3 holes total along the bottom , left and right sides, and the 5 hole will have 5.

Harry

Bringing Up Low Oil Pressure

Just a further follow up on my C90. My friend Don who is an AME came by and looked over the aircraft for me. He felt the oil pressure was a little on the low side still, so he put another washer in the regulator spring, which gave me a reading of close to 40psi cold or very close, which i have never had before. Today our oat was about 30 degrees or near enough 86 degrees farenheit, which is pretty warm. The oil temp remained well in the normal range and after a half hour flight, the oil pressure dropped to about 22 psi.

The battle i am having, is that my friend the ame thinks that is still too low but most of the people i know that have these old continentals tell me that 20psi is plenty for proper lubrication on a hot day.

I am currently using AeroShell 15W50 oil. Some have told me that i should be using a straight grade 80 oil since i don't fly the machine in the winter.
I would greatly appreciate your thoughts and comments on both the pressure and the viscosity of the oil i am using.

Installing washers under the oil pressure relief spring will only mask the symptoms of a leaking oil pressure relief valve, weak oil pressure relief spring or weak oil pump.  Ultimately, the oil pump will overcome the spring, and the pressure that the oil pump can produce is the pressure of the overall system.  Increasing pressure at the oil pressure relief spring is kind of like saying that a blocked artery is good for the heart because it makes the hard work harder, and exercise is good for the heart.  Eventually, you could install enough washers beneath the spring to the point where the relief valve simply never opens.  Tweaking the oil pressure relief valve can help to an extent, but there will be a point of diminishing return.

According to the Type Certificate Data sheet for the C90/O-200 the rated cruise oil pressure for the C-90 is 30-40 psi, and idle pressure is 10 psi. The O-200 lists 60 psi for the upper cruise limit.  So, the 22 psi you are observing is well below these limits.  .  Maybe it will operate ok at 22 psi, maybe not.  The point is, it is all a guess since there is no documentation to prove that the engine will operate safely within this range.

You can try a more viscous oil, as that will help increase the oil pressure. I have noticed that straight 50 summer weight oil works better in my A-65 than other types of oil.  However, I'm told by Aeroshell and Exxon that multi-vis oil will work equally as well.  I'm not sure if I totally agree as I have found that straight 30 weight works bets in winter and straight 50 weight works best in summer in my A-65.  On the other hand, I have an O-200 which has operated exclusively on Exxon 20w50 with no problems.

My apologies up front, but I'm fairly conservative in my answers when individuals are looking to justify operation of an engine outside of the documented parameters.  Given the facts at hand, the numbers indicate that your oil pump is not developing enough pressure to meet the performance specs found in the engine manual and Type Certificate Data Sheets. Ultimately, the solution to your oil pressure problem will probably be a replacement accessory case or an overhaul of the existing case.  You will probably spend a lot of time trying different oils, tinkering with the oil pressure relief spring, and worrying about low oil pressure until the pump finally goes kaput and needs to be replaced.

The oil pump is a chronic problem with the small Continental engines.  If you check the archive at the Bowers Fly Baby site of my Ask Harry questions, you will find quite a number of the same, repetitive answer regarding oil pump issues.

For your interest, here is a link to an explanation of the Continental oil system.  No solutions to your problem, but it does illustrate how the whole thing works.

http://150cessna.tripod.com/oilflow.html

Harry

A65 Starting Problems

Your problem will boil down to fuel or spark- it always does.  It is just a matter of getting both to occur at the same time.

Make sure that the magnetos are BOTH timed to right hand rotation, not left.  Also, physically remove the magnetos and re-install.  If the magnetos are timed to left rotation, the timing points will open at the firing point, but the distributor finger will be in the wrong place, giving the false indication that the magnetos are timed properly to the engine.  This is probably the number one problem related to non-starting engines after overhaul.  When I was working for Slick, I saw this not a few times, but thousands of times. 

Another comment on timing:  Reference the crankshaft timing marks on the crank using the crankcase split line at the bottom of the case.  If you reference the timing marks from the top of the case, and time to cylinder #1, then the engine won’t run.  Sometimes mechanics like to reference from the top of the case for convenience, but the crank rotates 180 degrees, so the magnetos need to be timed to cylinder #3, not #1.

Connect a spark plug to the ignition lead and lay the plug on top of the engine.  Crank the engine and look for spark.  When the engine is pulled through slowly until the impulse snaps, a spark should be easily visible.  If not, then check out the mags.

Next, the float may be stuck.  Give the float bowl a tap to jiggle the float loose.  If there is gas in the sump bowl, then there is gas coming from the tank.  If you have any amount of fuel flowing through the carb, then engine should run in some manner.  Even if the idle screw is misadjusted, the engine should run.

If you are having a hard time starting the engine, I would purposely flood the engine.  When a balky engine refuses to start, almost always there is a discussion as to whether fuel or spark is the issue.  If you purposely flood the engine to the point of having fuel run out of the carb, then you know fuel is present, so one variable is removed.  Once flooded, turn off the ignition switch, push the throttle full forward, and turn the engine backwards 20 times to clear the fuel charge.  CLOSE THE THROTTLE, and then go through the normal start procedure.  Lots of pilots have forgotten to close the throttle after trying to un-flood the engine, and then have been surprised when the engine starts up at full bore during the first starting prop blade.  An A-65 sounds exactly like an R2800 when standing six inches in front of the propeller at full throttle!

Another variable which you can control is the ignition switch.  Disconnect the P-leads from one or both magnetos to eliminate the possibility that the switch is grounding the magnetos.  When the switch wires were re-installed was the wire shielding lead attached to the P-lead?  This will ground the magneto and keep it from working.

During a non-start after a rebuild, the question of cam to crank timing always comes up.  I have never seen a mis-installed cam.  It doesn’t mean that it can’t happen, but I have yet to see it happen.  However, valve operation is easily determined by looking at the rocker arms relative to the timing marks.  Even if the cam is off a tooth or two, the engine should run, although not well.

Harry

Taper Hub Will Not Come Off

Can you please help?  I have torn down an A-65 and have the crank out of the case. The taper hub refuses to come off!

I took it down to my local automotive shop we carefully we put in the press and applied some pressure (prop hub nut threaded all the way forward) but nothing (also the bars were right up against the shaft to avoid any stress on the hub flange). Heated the hub lightly with a propane torch not super hot but enough that I thought for sure it would pop loose. Again nothing. Affraid of damaging the shaft or hub we stopped.

What can be done now?

Did you remove the snap ring?
 
Here are a couple of articles on removing the Continental tapershaft hub:
 
http://luscombe.org/index.php?page=continental-taper-shaft-crank

http://vintageaircraft.org/featured/2005%20-%20Vol.%2033,%20No.%2003%20-%20Type%20Club%20Notes.pdf

Both of these articles pretty much detail how to remove the hub.  If the hub won't budge, then be patient.  Soak the hub in a penetrant oil for several days and go through the heating process a few more times.  The hub will eventually come off.

Harry

Crank Grinding (Follow-Up to the Above)

No I never removed the snap ring. When it was in the press the nut was turn all the way forward. My thought was there was about 1/16 to 3/32 gap that would allow the hub to pop loose.
 
It came off tonight using the technique from the second article, I made the tool to keep the snap ring engaged that allowed me to get enough torque on it and with a little heat it came right off. To my surprise there was no rust just shinny metal on the taper!

This shaft is already .010 under, to grind or not to grind would be my next question?

Measure the wear of the journals on the crank at four points to get a feel for the eccentricity or how "egg shaped" the wear pattern of the journal is. Also, inspect for the depth and pattern of any grooves in the journal.  You can get away with some grooving, but not much.  Sometimes the grooving or surface irregularities can be polished out or diminished if it is not too bad.  The point is, once the crank is ground, that metal can never be replaced, and A-65 cranks are no longer manufactured,  so I reserve grinding for a crank which simply cannot meet service limits.  It probably took 20-30 years for this engine to wear out, so a service limit crankshaft has the potential to provide plenty of years of service.  Of course, if the crank is worn too much, then it will require grinding.

I usually do not ask the opinion of the crank grinding shops as to whether a crank should be ground or not.  Their business is to grind cranks, so the answer is always yes.  Get several opinions on the condition of your crank from local engine shops and mechanics and proceed accordingly.

Harry

A65 Upgrade to 85HP

I am re-building a 1941 J3 with a 65 HP engine. I would like to upgrade it to a 85HP engine with a starter. I would like to find a case and have the engine built. I would possibly also be interested in the 100HP STC so the case would need to be able to use that STC. Three questions. What is the correct case and how can I find drawings for the electrical system and does the electrical system require an STC.

If your plan is to use a lot of the internal parts from the A-65 to build a C-85 be advised that  not much is useable.  The cam, rods, crank and cylinders are all different than the  C-85.  You can build up an engine from piece parts starting from just a case, but this is fairly expensive, also. The best bet is to find a complete C-85-12 and work from that as a start. Even a complete, runout engine will yield lots of the small parts which really drive the cost of an overhaul up.

Technically, there is no 100 hp conversion for the C-85.  There is an STC to use an O-200 crank, rods and pistons, but the engine is still rated for 85 hp.  The O-200 crank conversion is reported to make the C-85 run stronger because O-200 internals are used.  However, the C-85 is rated at a lower 2575 rpm than the higher 2750 rpm of the O-200, so the only way to get the C-85 to make 100 hp is to run the rpm illegally high at 2750.  The cam of the C-85 is also a bit different, but I don't know what effect that has on engine performance.

The C-85 -12 is the best choice to consider when converting from the A-65. The motor mount configuration is the same between the A-65 and C-85, so the C-85-12 will bolt directly in where an A-65 fits.  The O-200 has different motor mounts, so the conversion requires either a completely new motor mount or modifications.  The prop from the A-65 can be legally altered to work with the C-85, but, in most cases, is not approved for the O-200.

The electrical system info would need to be obtained from a Piper Cub interest group, such as the Cub Club, www.cubclub.org.

Harry

Engine Locks Up when Hot

MY BUDDY JUST PUT ON 4EA OVERHAULED YELLOW TAG CYLIDERS AND PISTON FROM A OUTFIT EL RENO OKLA,LESS THAN 1 HR TOTAL RUN TIME 30 MN GROUND RUN 2 FAILED FLIGHTS THE ENGINE LOCKED UP WHEN HOT AFTER 4 MIN 2100 RPM,AFTER COOL DOWN THE ENGINE WOULD ROTATE.HE PULLED THE JUGS AND 3 PISTONS WERE SCORED.THESE WERE SUPPOSEDLY RECHROMED AND FITTED BY THE CYLINDER SHOP.I KNOW I HAVE NO PARTS OR PICS BUT WHAT ARE THE KNOWN ISSUES WITH RECHROMED CYLINDERS  

It sounds like the wrong type of rings were installed in the chrome bore cylinders.  Steel bore cylinders require chrome rings and chromed barrels require cast iron rings.  If chrome rings are installed in a chrome bore, the friction will be too high and the end result is exactly as you have described:  severe scoring and eventual lock-up of the pistons in the bore.

Harry

A65 Excessive Fuel Burn

I fly a Pietenpol that I built with an overhauled A-65-8 with 400 hours on it.    I would really appreciate any insight into a head-scratcher that has been bothering me-- excessive fuel burn this summer.   

Normally I burn 4.3 gph @ 2150 rpm, now I'm burning upwards of 6.0 gph.    3 years back I leaned the mixture control  by saftying it about 1/4 the travel leaner than full rich.  That reduced my burn at the time from 4.6 to 4.3 and that held fine for many hours. 

This summer I've had carboned plugs and the high fuel burn so I played with the mixture lever position to further lean  and this resulted in stumbling on takeoff power application.  The carboning (as it turned out) was due to a rich idle  mixture setting.  I went back to the trusty 1.5 turns out from fully closed (after I lapped the needed to make sure there were no burs or grooves)   Now the plugs burn clean and I ended up putting the mixture back at the 1/4 the travel from being full rich.  

Engine runs strong, compression is good on all four, Eismann mag timing is correct at 30 deg. btdc, and all plugs  are firing and gapped properly.   I have no induction air leaks that I could find, the foam air filter is brand new (excess oil squeezed out before installing) and the  carb has been modified to the yellow dot configuration (in 2001) to included the weighted float and new idle (#60 drill ?) hole with the former being plugged by a lead ball.  

I'm hoping to fly the plane to southern Indiana to Lee Bottom for the Wood, Tailwheel, and Fabric fly-in this Friday  but don't feel 100% comfortable with the high fuel burn.   I have a 17 gallon tank so I could easily make the trip  but.....I would greatly appreciate if you could share any thoughts on what might be happening here.

PS-- when I safety the mixture lever it pulls 'down' against the tiny spring on the shaft so the lever isn't floating as it does with no downward force--not sure if I'm doing any harm/foul here or if I should safety it so it doesn't bottom out the spring/mixture shaft downward.

Your e-mail heading indicates NAS5, but I am assuming that you meant to type NAS3 for the carb model.

First, the mixture control on the Stromberg NA-S3 carb does not function like the mixture control on a Marvel Schebler carb in terms of the range of leaning capabilities.  The Stromberg carb is by design a auto-leaning carb and the so called mixture control just fine tunes the operation of the leaning circuit.  Throughout the full range of travel of the mixture control you will only see a slight change in overall fuel burn.  In effect, the "mixture" control is relatively useless. 

Once the airflow through the carb is out of the idle circuit (typically above 1000 rpm) then the metering jet manages fuel flow.  The jet would have to be oversize or leaking a lot for an extra couple of gallons to go through the carb.  If there was that much fuel going through the carb, there would either be stains from un-consumed fuel or extremely sooty plugs and exhaust. The signs should not be subtle.  If the fuel float level was too high, gas would pour out of the carb when the plane was parked.  The size of the metering jet and the mass of airflow through the carb generally determines how much fuel will flow through the carb.  In other words, only so much fuel can physically flow through the carb due to demand, but much more fuel than required can leak out of the carb.

If the airflow through the intake was reduced, then the engine could run rich, but it would also be down commensurately on power.  Normal thinking would suggest that a blocked intake would not result in an increase in fuel flow, but more likely a reduction in power and sooty plugs.

Check to make sure that your primer (if installed) is not leaking (although a leaky primer is more of a problem at idle).  I would simply disconnect the primer, cap the inlet with a rubber vacuum cap which you can get from any auto supply store.  Run the engine, see if the fuel burn stays the same.  By the way, an indicator of a leaking primer is sooty, fouled spark plugs.

On the engine side, an intake leak can result in high fuel consumption.  Any leakage at all through the intake valve is not allowable, so do a compression check to see how the valves are sealing.  By the way, the intake valve can warp and stop sealing due to excessive leaning.  On Cubs, the front cylinders tend to develop intake leaks, maybe because of the in rush of available cooling air and rapid differential of heating and cooling of the cylinder head.

Another very likely possibility is that fuel is being siphoned from your tanks during flight.  This should be kind of obvious due to fuel stains on the wing, but maybe not.  I have seen this as a problem before.  Have you done any recent work to the fuel system?

Harry

Follow-up from Harry

Here is some additional info.  The following is lifted from the Aeronca Aviators discussion and is authored by Bill Pancake, a well known and
respected Aeronca expert.  Bill is the expert I go to for difficult questions:

Your problem is probably in the throttle body.  A brass tube (.152" in diameter) leading from behind the venture to the mixture chamber can become partially clogged with dust, dirt,  and sometimes flock from the Airmaze Airfilter.  This tube operates at a negative pressure and when it becomes partially plugged it creates a negative pressure in the float chamber.  This will cause the engine to run lean and when you apply carburetor heat it causes the mixture to become richer.  Most likely the engine will at times run normally.  To correct this problem remove the top of the carburetor and using a pipe cleaner (ones the pipe smokers use to clean their pipes) with some solvent on the pipe cleaner pass it through the tube.  Next blow out with compressed air and this will eliminate all the blockage.  Most of the time when carburetors are rebuilt they are placed in gunk and the real problem is never identified.  I have encountered this problem on several occasions and by using the  above procedure was able to correct the problem. I highly recommend doing a complete overhaul of the carburetor any time that it has been disassembled.  Go by the manufacturer's book. 

Harry

Follow-Up Question

Thank you so much for you response Harry.    All excellent points and well received.  

I did a careful refilling of my fuel tank last night after a 1/2 hour flight at cruise and I found that I am burning just under 5 gph.  Last summer I was in the 4.3 to 4.5 range.   (2150 rpm)   

I don't have any primer system and all intake rubbers and gaskets/spider/carb seals are good.   The compression is good on all four cylinders (tho I have had leaky intakes in the past on those two front cylinders--but that is corrected)    The plugs are burning clean too.   (They were sooting up but I had the idle mixture too rich and they were fouling just taxiing around) .

The carb doesn't leak a bit parked and I'm happy with that (fuel valve open) as I have a steel needle and seat.   No fuel stains on the belly that I can see and my nose tank/cork and wire doesn't siphon---but all great points of possibilities. 

The only work I've done on the fuel system recently was to replace my gascolator gasket and the screen was debris free.

I'm heading south to that fly-in Friday in near Louisville, KY and am going to mark my cork wire with marks to show me 2.5, 5.0, 7.5, and 10.0 gallons burned marks so as I fly I can be assured that my fuel burn is as I measured last night.

I have 17 gallons total with 15 useable so I'm okay there---I'm just being anal about having a greater fuel burn than I used to.

Guess I'm just envious of the guys who have A-65's that burn 3.8 gph !

One more thought.  Is your tach accurate?  If it is reading 2150, but actually turning 2350, then your engine would appear to burn more fuel at a relative rpm.

Regarding the 3.9 gal/hr fuel burn, see the comment above.  It could be that this is a false number.  75 years of collective tribal knowledge on this engine supports about 4.5 gallons/hr as normal fuel consumption.
 
Harry

No Generator Output

Hello Harry. I was wondering if you could help me? I have just reinstalled my starter and generator back on my continental c-90-12f ,they have both just been overhauled. My problem is that it is not showing a charge on my amp gauge but shows a discharge when I turn anything on. I'm pretty sure I have it wired right, but don't have a wiring diagram. I've heard I may  have to excite the field? If this is true how do you do it? The engine is in 1956  Aeronca 7ec champ.

It is common to "flash the field" of a generator to excite current flow. Disconnect all of the wires from the generator.  Locate the terminal marked "F" for Field. Using jumper cables, connect the "-" negative lead from the battery to the engine.  Connect the "+" lead to the positive connection of the battery.  Quickly tap the positive lead to the "F" or Field stud to excite or "flash" the field.  Just a quick tap does it and a spark may occur, but don't connect the positive lead or dwell too long.  Reconnect all of the wires, start the engine and look for amp output.  If no output, then repeat the process.  Avoid sparking too many times at the Field stud as the sparks can damage the stud threads.

Harry

More On Low Oil Pressure


Harry, I have an Aeronca 7AC with an A-65-8 Continental. I'll try to make this long involved story brief. I overhauled the engine and everything was fine. 125 hours later I developed a crack around the number 2 cylinder. It could not be repaired. I got a case for the A65 from a friend and sent it off to ECI for refurbishment. I got the case back and installed all of my parts into that case. Right from the start, I had low oil pressure once it warmed up. 40 psi at startup and 18 psi at 175 degrees in cruise. My old case had 40 PSI at startup and never went below 36 PSI in cruise. I flew it this way for about 5 or 6 hours then I couldn't stand it anymore so I tore the engine down again. A very good friend is very good with Continentals and he helped me, but not before checking my accessary case and oil pump gears. All seemed fine. I bought new bearings and used plastigauge on everything before reassembling my engine. My Main bearing and rod bearing tolerances were smack in the middle of the specs. The cam journals were on the upper side of the spec at .005. Keep in mind that I used the same accessory case that was giving good oil pressure with my old case. I have the same results.....40 at start-up and 18-20 when oil temp reaches 175. How frustrating. Do you think the cam journals being on the high end of the spec is causing my problem. Several friends have told my to quit worrying and fly the plane. It is running like a top, but I can't quit looking at that oil pressure gauge. Thanks in advance for any advice.

As you are finding, oil pressure problems a continuous thread of discussion with the Continental A-65 series of engines.


A couple of the chronic problem areas of wear in the case which affects oil pressure is the cam journal clearance and the clearance between the tappet bodies and the crankcase.  If the tolerances become too great, then the engine can lose oil pressure as the oil warms up.  However, I would think that if the tolerances are within the range spec'd in the manual, then you should not have a problem. 

It could very well be that your oil pump is the culprit.  Here is my convoluted thought on this:  The tolerance stack up of your first engine may have been such that the pump may have been able to produce enough pressure for the overall system.  With the "new" engine, maybe the stack up of tolerances is tighter overall, and the oil pump cannot maintain the increased demand.  Just a thought.

I have had similar problems in the past, and I keep swapping parts around until I get a better result.  The oil pumps can be finicky and I have had a pump work great and then suddenly not work.  You may want to inspect the pump and retorque the cover plate.  It is very common for the plate to warp slightly and re-torquing can help to get the edge seal tolerance back on the pump. Also, check your gauges for accuracy.  Sometimes this is part of the problem.

Another thought:  does the oil pressure relief spring have a bunch of washers between it and the valve to increase the pressure of the spring?  If so, then the pump is probably weak and the washers have been installed to band-aid the problem. 

Finally, are you using 50 weight oil or multigrade?  I'm not sure why, but I see more complaints about multigrade oil and low oil pressure than straight weight.

As far as the low oil pressure goes, I can only quote the book specs and your engine should develop 28 psi at cruise.  Low oil pressure is low oil pressure, so if it is not in spec, then there is a problem or a developing problem.

My opinion is that the oil pump is probably the culprit, though.

I wish I had a better answer, but welcome to the club.  I get probably a dozen e-mails each month about low oil pressure.

Harry

C-85 Pistons in O-200


I am looking for the part # for the c-85 pistons that will fit in the o-200 continental engine.  At least that is what I think I want.  I'm having my engine rebuilt for a PA-11 cub. I would like for it to have a little more power without sacrificing the reliability.

The way I understand it,  I can't just use standard c-85 pistons because there isn't sufficient valve clearance,  so I need the ones that are already notched to allow for sufficient valve clearance in the o-200 engine.

Finally,  I thought the compression ratio on the standard o-200 was 7:1 and the compression ratio on the c-85 was 8:1, does that sound about right?

Be aware that the C-85 pistons are not legal to install into a certified engine.  If the pistons are installed into an experimental engine, a specific logbook entry must be made noting the change, an FAA Form 337 filed to inform the FAA that the engine is being converted from standard certification to experimental, and the data plate needs to be removed from the engine.

The p/n for the C-85 piston is 40327.  The piston needs to be modified with a ¼” wide, 45 degree chamfer at the piston crown to clear the edges of the cylinder combustion chamber.  However, the cylinders vary, so some experimentation may have to done to get the right fit.  The mod bumps the compression ration from 7:1 to about 7.8:1 and theoretically will add about 4-5 hp.  The C-85 pistons will make a bit more power, but the change is not a major gain.

Harry

Propeller Bolts

What is the correct propeller bolt for a McCauley CM7148 propeller bolted to a C-85-12 engine? Currently I have AN6H-32A but the thread end does not go completely through the flange.

Here is a link to McCauley propellers.  No info on the torque, but there are contact phone numbers.

http://www.mccauley.textron.com/home.html

The Sensenich site is more useful:

http://www.sensenich.com/

It sounds like your bolts are too short.  Usually, the FAA requires two threads visible where the bolt passes through a fastener.

Here is a link to Sensenich's bolt length info page:

http://www.sensenich.com/engineer/boltsize.htm

Harry

A65 Quits on Landing/Carb Leaking


I have a cont 65 that quits on landing, just after I landed, after playing around for an hour, doing t&go's, we landed at another airport, the engine decided to quit after we landed. it would not run, unless the rpm was at least 1,000 or so.

I checked the screens, on the bowl and the carb, and found nothing that would stop the engine. I re-checked all the rubber tubes. they seemed ok, I also checked the primer, everything ok there also!

Any idea what the problem could be??

I also want to increase the horse power as much as I can, I understand there is a 75hp carburetor kit for the 65, where can I find something like this??

The carburetor leaks like a sieve, if I leave the valve on, it will drain the gas tank empty, how do I fix this? Do you know of any shops that can fix this carb, or exchange it for a carb that is set-up for 75 hp, even though it will be on a 65 continental.

First, your comment on the leaking carb is of concern.  It sounds like needle is not sealing in the float bowl, which is an indicator that the float level is incorrect, the float has sunk, the float may be sticking at the hinge point, or the needle tip has disintegrated.  I would ground your plane immediately until you get this problem sorted out.

Regarding the engine stopping, it is very likely related to the problem above and the carb is literally flooding out with fuel.  There is the possibility that the idle mixture is not set right, but I'm pretty sure that the problem is with the float.

Another possibility is that the magnetos have worn carbon brushes or cams. Unison has just issued a couple of major Service Bulletins on this topic. Without going into a lot of detail, if the point cams or brushes develop too much wear, then the magneto may not produce any electrical current at low rpm.  In the worst case, the engine may stop because both magnetos cannot produce any energy.  The Slick Service Bulletins detail that these failures can occur in as little as 15 hours, so you could experience problems in a very short period of time.  I've attached the Bulletins.  This is a recent problem and I have experienced all sorts of problems with the Slick mags in recent months.

Slick Service Bulletin SB2-08
Slick Service Bulletin SB3-08

Regarding a carb overhaul, I highly recommend Aircraft Systems in Rockford, IL, phone 815-399-0225.  They are one of the best shops I have worked with and they understand the Stromberg carb.  They can also look at the mags, but they will charge you, whereas I am free, but busy for the next few days.

Finally, I have attached a Service Bulletin which details the conversion from an A-65 to A-75.  Refer to page 9 for the parts required.  The conversion adds a bit to the rate of climb, maybe 50-75 fpm, but that's about it.  You will notice a little bit stronger engine, but not a kick in the pants.  Me and the two other guys with Champs at my airport are installing C-85 engines to replace the A-75.  The C-85 really makes a big difference, but is more costly.  The 65 to 75 conversion is easy and involves a piston change, some mods to the connecting rods, gaskets and a prop re-pitch.  In terms of climb, I have found that a climb pitch on the A-65 works pretty good, but the cruise on the Champ drops to 72 mph.

Harry

High-Revving O-200

I have a Jodel D11with a 0-200... I recently replaced a very old cylinder  (1200hrs) so now I have 4 new ones ( previous owner replaced 3!) To make the package as good as it could get I decided to replace the (35 year old) hand made prop....Great you might think?   I had Richard Sweetapple manufacture me one from a blank he had ( EVRA copy)  I just fitted it.  Only problem is, the 0-200  will easily overspeed at max throttle in level flight....That is, the engine will reach 2700rpm comfortably and quite quickly....I don't think anything can be done to increase the pitch ..... So I am stuck...  ( with the old Bishton  prop I couldn't get over 2600rpm in level flight) .. I had the engineer that fitted the new ( Millenium) cylinder alter the timing to 28 degrees BTDC... So the question is...Just how high can I rev the Continental without damaging it? It has 1200 hrs on it..Very many  Europeans use the EVRA prop for Jodels, BUT now I read that there are TWO models,  one fine pitched and  one standard...Guess which one I have?. I used to have a 100knot cruise which took 5 minutes to stabilise...........Now its down to just over 90 ......at 2600rpm  almost instantly.....Any Suggestions ( apart from burning the new prop?)

The O-200 is rated to run at max continuous 2750 rpm.  By your description, it sounds like you are hitting redline rpm to the limit specified by Continental.  So, I don't see any issue other than you are probably going to climb a bit better with a slightly reduced cruise.  Since the engine is not rpm limited, you can just turn higher rpms to make up for the cruise, although you will burn more fuel.

Harry

More Hot-Starting Problems

I have owned a Reims Cessna 150H for some 9 years. A trusty stead in most respects but the engine is difficult to start when hot!  The engine, Constructor's No 24 R 896, has done 788 hours since a major o/h. Power and compression are both good and cold start is instant!  Your advice on the best hot starting procedure would be appreciated.

The O-200 should start about the same hot or cold.  Of all engines, the O-200 is certainly not regarded as hard to start under any circumstance.  So it is fairly safe to assume that there is a mechanical problem of sorts.

I would inspect or simply replace the accelerator pump on the carburetor.  I have experienced this problem before and replacing the accelerator pump was the cure.  This is a tricky problem to solve as the accelerator pump may actually squirt fuel into the carb throat when the throttle is pumped, but the pump can leak internally and the carb will run very rich and the engine can burn as much as an extra gallon of gas per hour.  If the pump has completely failed, then no fuel is pumped into the carb during start.

Another possibility is that the venturi is loose or deformed, but this would result in fairly poor engine operation in all regimes.

The magnetos may be a cause, but doubtful.  Both magnetos are identical and are impulse coupled for starting.  Both magnetos would have to fail in an identical manner to affect starting.  Not impossible, but unlikely. However, the magnetos are easy enough to inspect to ensure that internal timing is correct and the coil and capacitor are at rated specs.

Harry

Connecting Rod Nut Torque

Hello Harry, I'am in the process of overhauling my Tcraft A65-8. My engine manual has no torque values for the connecting rods nuts, perhaps it's a very early Manual. The C85 Manual with a size 3/8-24 nut for the connecting rod shows 400-420 in. lbs. Should I use these torques for my A65-8 ?

For some reason, old versions of the A-65 manual do not list a specific torque for the A-65 connecting rod nuts.  The bolts and nuts are the same as used on the C-85 through O-200, so the torque value found in these manuals will work.

However, Continental has published Service Bulletin SB96-7C which lists all of the torque values for every piece of hardware installed on every single Continental engine.  SB96-7C, page 5 lists the torque for the A Series connecting rod to be 400-475 in lbs. 

Here is a link to this publication:  http://www.tcmlink.com/pdf2/SB96-7C.pdf

Harry

A65 Top Overhaul

I am looking at an Aeronca Chief. Nice looking, new cover and interior.  My problem is that the engine has 1618TT and 91STOH. Why would someone go through the expense and trouble of doing a top (if it was indeed a top) on an engine that close to TBO?  Should I be afraid of this thing? Or, are the lower ends of the A65 that bulletproof that a good top is enough in this case?

With an engine like this, the first thing to do is to set the logs aside and inspect the "as-is" condition of the engine.  You will need to check the compression, oil consumption history, oil pressure, and overall external condition.  A parts list or work order from the top would be useful, but I expect that you will find that the cylinders were not yellow tagged. Probably, there is simply a logbook entry that the engine was topped, and it is likely that the owner did the work and a mechanic signed it off.  While legal, this type of work may not add up to a proper top overhaul.  I would be more concerned if the top was only a couple of hours old, indicating that the owner patched it up to sell.  Given that it has 90 hours, this indicates that it was flown successfully for some period of time.  If you inspect the engine as if it were an annual inspection you should get a feel for if it is good condition at this time.

In terms of the long run, who knows?  I owned a Cessna 150 which had an O-200 engine which ran to 3800 hours with no parts replacement at all!  The engine in my Swift only has 750 hours since new, but needs to be overhauled as it has not been opened up for more than 55 years, uses a quart of oil every three hours, but generally runs great.  Engine TBO numbers are the manufacturer's recommendations, not necessarily the exact point at which an engine is required to be overhauled.  Engines may require overhaul or service sooner than TBO or may run well beyond TBO.  There is no guaranteed formula, but consistent maintenance and frequent flying will generally result in a good engine.  At some point, this engine will need to be completely overhauled, but as long as it is running ok, the hours are kind of irrelevant.  Inspect the engine for condition, and evaluate the operating trends to this point.  If you buy this aircraft, just keep track of oil consumption and compression trends to establish an operating history of this engine.

Harry 

Telling the A65 Case from the C-85 Case

I  just purchased one "lot" of engine parts.  One case is an A65-8 bare case with a data plate, no issues there.  There is a A65-8 case with no data plate, with a tapered crank and a A65 cam, no problem there.  The third engine is a little bit of a puzzle.  The case has a hand made data plate and the  manufacturer is LAWSON CONTINENTAL with a serial number and 85 hp with 3100 rpm max stamped in it The gentleman that I bought if from stated that it was a regular C85 case.  This engine is complete minus mags and carb. There is a flanged crank but the number 3 rod journal has a spun bearing. The cylinders are 85/ 0200 as they will not fit in the 65 case but the bolt hole pattern is the same..  However the case for the third engine looks identical to the A65-8.  My question is, how do I tell a C85-8 case from an A65-8 case, and are there any marks to identify the crank? I have seen in your postings that it would be possible to machine a A65 case to accept C85 cylinders so I am wondering if someone followed your instructions.  This engine came off of a Zenith 710.  Any information would be appreciated.

For the most part, the main difference between the A-65-8 case and the C-85-8 case is the size of the cylinder bores.  The 65/85 bolt flange is the same, but the OD of the A-65 is about 4" whereas the C-85 through O-200 is about 4.25".

As for the data plate, I'm pretty sure that I have the answer.  If a type certificated engine is modified from its FAA approved configuration, then the FAA requests that the OEM data plate be removed and a builder fabricated plate be manufactured.  It appears that you may have an engine off of a homebuilt which has been modified in some way to change it from its Type Certificated form.  The Formula 1 racers like to add an extra through stud in the case of the C-85 and re-indexing of the cam is not unusual.  It could be that the builder of the Zenith simply built an engine from parts and made up his own data plate.  You should inspect this engine to make sure that it can be returned to a stock form.

Harry

Crankcase Sealing and Breather Tube

Harry, I'm about to join the case halves, just would like your estimate on the gap that is needed in the rough portion in the casting just above the top rear stud over the large main bearing.  I was considering sealing it closed to prevent oil spray from getting close to the crankcase vent, but I have been told that would cause more oil to escape out the vent hole. I suspect that the vertical cavity that has the vent at the top tunes up when this casting gap is sealed. A gap is needed to equalize the crankcase pulsations at the vent hole as a smoother vent gas flow would carry less oil droplets out the breather vent hole.  I am familiar with elbow extensions etc.   Gap is now about .10" 

I would be hesitant to use any extra sealer in the internal engine case for the simple reason that it is likely to break loose and drift around the engine internals.  It is not unusual to have oil galleys get blocked due to stray sealant material which can lead to oil starvation and subsequent bearing failure.  I don't think that the oil splash in that area has a significant effect on oil blow-by through the vent tube, anyway.  The main source of the oil is simply film oil on the case interior.  By moving the vent pickup into the "vaporized" oil area into the case versus the "wet" oil on the case, this alone should be sufficient to greatly reduce oil blow-by.

Another consideration is that this gap may be part of the design of the engine.  Attached is a photo of a C-85 case in  the area I think that you are describing.  You will see a pencil pointing to the gap just forward of the top, rear main stud location.  If you note, I have an extended, fish mouthed breather tube just to the left of this location.  Just to the left of the forward stud, you will see a channel which extends down to the oil seal.  If you look at this bearing area in detail, you see a clear path of oil through the gap at the top rear, main bearing stud, to the oil seal and to the bottom of the case.  Right or wrong, it looks to me like these gaps do serve some sort of purpose in the oiling system of the engine.  Based on that, this would be another reason I would be hesitant to close up the gap.

I think that you will find that the extended breather tube will provide a lot of relief from oil blow-by on its own.

Harry

Follow-up

Harry, thanks for your response, I agree with not sealing up the breather wedges. I have not heard them called that before, but I need to call them something as  I think there very important.  I am now curious about your fish mouth breather extension, would you share a sketch ? 
 
Here are some additional pictures of the breather tube.  Note that when thefish mouth is horizontal, the breather outlet extends slightly upwards and will guide the vent tube over the top of the cylinders.  With the outlet angled upwards slightly, the case can still vent, but the velocity of the oil droplets and vapor will slow due to all the right angle turns and effects of gravity.  In concept, the oil will coalesce and drain back into the case.  The net result should be less oil blow-by.  Probably the simplest, lowest cost air/oil separator on the market.

This vent tube is made by Bill Pancake, Route 4, Box 218, Keyser WV, 26726, 304/788-1974.  Bill is an extremely knowledgeable fellow with Aeroncas and Continental engines- he is an expert's expert!



Harry
 

Backfiring at Idle

My A65-8 has recently started backfiring at idle or a little above idle. I have been using autogas but recently started using half autogas and  half 100 LL. Could this have anything to do with the backfiring?  The engine runs fine at higher RPMs.

The backfiring is probably not related to the fuel, but could be due to the onset of Fall and slightly lower outside air temperatures.  When the outside air temp cools, the intake air density increases, therefore more fuel molecules are required to match the increased ratio of oxygen molecules. The carb idle mixture usually requires some minor adjustment from colder to warmer weather (and vice versa) to prevent backfiring, especially when the throttle is closed or when the engine is windmilling on an extended glide. Usually, the idle mixture is too lean if the engine pops a bit when the throttle is reduced when landing.  The idle circuit is not effective above 1000 rpm, so the main metering jets take care of fuel flow and the engine is not likely to backfire when operating at higher engine rpm’s.

At the back of the carb body is a slotted set screw with a tensioning spring between the screw and the throttle body.  Turn the screw clockwise to lean out the mixture and counterclockwise to enrichen the mixture.  If the engine is popping, then the mixture is too lean, so the screw should be turned in a bit counterclockwise to enrichen the mixture.  There is no set amount to turn in the mixture screw, so just experiment with ¼ or ½ turns to get the mixture set right.  I just adjusted the carb on an A-65 installed in a Champ and it required nearly 1 ½ turns to enrichen the idle mixture. 

Harry

Aligning Gears in Slick Mag

Harry, I took apart my left mag to adjust the points (Slick #4333) and I don't know how to line up the plastic gears.  I took it apart because I was getting some backfiring thru the exhaust on the left mag. I obviously screwed up the alignment of the plastic gears.

The points had about a .10 -.12  gap when I started and about a .26 gap when I adjusted them according to instructions I found on the 'net. I don't have Slick's special T-150  tool, but I used a wire & it had to be pretty close. Then I also saw on the 'net that the gap should be between .15 & .19, so I set the points at .18.

Ok, first problem is that the point gap will be about .008" to .012" when the cam is at the highest point of lift.  The .26 gap is waayyy too wide and the Slick mag simply won't work.

The 4333 is a RH rotation magneto, so the mark on the small gear labeled "R" is aligned with the metal tab on the coil.  The big block and gear is pinned using the T-118 timing pin (or equivalent) to align the R timing marks found next to holes in the distributor gear and distributor block.  Insert the timing pin or equivalent through the holes to "pin" the parts marked R in alignment.  Slip the distributor block assembly onto the mag frame and the line marked R on the small gear should align with the groove in the distributor block.

Once the mag is re-assembled, leave the timing pin in the R hole of the block, set the engine up to the firing point and install and time to the engine.  Both magnetos are pinned for RH on this engine.  IF you pinned the left magneto for LH, then the engine won't run very well.

Harry

VWs on Fly Babies

I'm inquiring about possibly using a VW engine with redrive and also about building a fly baby as a bi-plane?

That certainly got my attention as I love bi-planes! :-) What would the useful load be on a biplane?

Check out www.bowersflybaby.com for load and weight carrying information on the Fly Baby.

The VW re-drive is still probably not enough engine, especially for the draggy Fly Baby bipe.  A typically VW redrive displaces about 2180 cc, or about 133 cubic inches.  A Continental A-65 is 170 cubic inches and a C-85 is 190 cubic inches.  So, a VW 2180 cc redrive has 28% less displacement than an A-65.  The 2180 VW has a similar bore to the A-65 , 3.622" VW to 3.625 A-65, but the stroke of the VW is much shorter, 3.228" to 3.875" for the A-65.   That works out to about 20% less stroke for the VW redrive.  A long stroke is the key to developing torque, and torque, not horsepower, drives the prop.

The VW makes up for lower displacement by developing power via more frequent power cycles over a given time and movement of the crankshaft, otherwise known as RPM.  The A-65 makes its max power at 2300 engine rpm and the 2180 will make its rated horsepower at 3200 rpm.  So, assuming that the 2180 VW redrive and the A-65 are rated for 65 hp,  the A-65 will make its power with 39% fewer rpm over any given power setting.

But, the real measurement is thrust, and the diameter and pitch of the prop is as good a method as any to determine thrust.  Consider that a standard wood prop used on an A-65 powered Piper Cub is 72" in diameter and 42" in pitch.  Give or take an inch or two, the prop diameter and pitch from any engine needs to drive a prop of about these numbers to pull the Fly Baby. Propeller disc area is the deal breaker from most automotive conversions. To turn the higher rpm required to make the horsepower number, the prop needs to have a smaller disc area in order to allow the engine to turn up rpms.  On the flip side, the four cylinder Continentals are too heavy for some homebuilt applications and the prop can't be made small enough diameter to still produce adequate thrust within a reasonable rpm range.

I have flown behind a number of Subaru, VW, and Jabiru engines.  No question at all, the A-65 through C-85 series Continental has more pulling torque than any other engine in its horsepower class.  The A-65 is also a less complicated installation- basically a motor an prop.  No coolant systems, no belts, no electronic gizmos.  Just simple, with fewer things to break.

There have been a few Fly Babys built with the smaller displacement Lycoming O-145 and Corvair engines, but there always seems to be the feeling that these engines just are not quite enough for the Fly Baby.  In the end, cubic inches and torque always wins. 

Harry

[RJW Additional:  There is a PSRU available that does permit the VW to turn at its maximum HP RPM while keeping the propeller RPM in a very good range for a Fly Baby.  However, as the Fly Baby List's VW-engine Guru (Robert Hoover, aka "VeeDubber") points out, the VW engine's primary drawback as an aircraft engine is its ability to dissapate heat.   It's an engine designed for long-term loafing at 35 HP or so; trying to force it to produce more power makes it run hotter.  Sure, you can put bigger cylinders on it to produce more power, but you're still stuck with the joined cylinder heads, relatively shallow fins on the cylinders, etc.

My basic advice about putting a VW conversion with the new PSRUs on a Fly Baby:  Wait until you see one of the converted VWs fly on an airplane originally designed for an A65, or even better, a C-85.  So far, the only airplanes I've seen them on have been designed around the engine.  If you see, for instance, a Pietenpol or a Baby Great Lakes flying nicely with one of these conversions, that's a good sign that the conversion will work on a Fly Baby.

Finally, the Fly Baby biplane is draggy.  It really needs a bit more power.  I'd prefer to see C-85s on them rather than A65s.]
 

Slick Magneto Studs

I have an A65 and am trying to install a set of slick magnetos with impulse units that came off another A65. The studs are too short indicating to me that it had non impulse mags installed. I have been looking, starting locally and now 2 full days of calling around the country, trying to find the longer studs, the small clamps, and nuts to install the mags with. Not one company or person has them or knows where to get them. Do you have a source you could recommend? It seems like such a simple parts set.

The studs are a part number M2369 and was a special part made by Slick.  The only chance of finding these is to call Aircraft Spruce or Aviall. Probably, no company will have these in stock as it is a small part, but you may get lucky.  Slick Aircraft Products was just sold to Champion and is in an upheaval right now due to the transfer of assets and new part orders at this point in time (Oct 08) are not happening.  Not a pretty picture, but accurate with no false hope which will just make you more aggravated. 

I seem to remember that the M2369 stud is threaded for a standard coarse thread where it inserts into the case and was fine thread at the nut and clamp end.  Lycoming makes a nearly identical part under p/n 61668.  I think that the Lycoming part may be coarse thread at both ends, which really doesn't make a difference.  The Lycoming spec for the stud is 5/16 x 18 thread.

Harry

Still More Low Oil Pressure

Harry, thank you for the enormous amount of knowledge you are willing to share!  I've got a C-90-8 with kind of your classic oil pressure problem, with one big difference!   The engine has just been overhauled by Custom Airmotive in Tulsa; it had the accessory case sent to Drake Aviation for re-machining, and on Custom's test stand, it performs flawlessly, with the oil pressure running right at 40 psi with 190F on the oil temperature.

HOWEVER-when we put it on the airplane we can not keep the oil pressure up to an acceptable level-after about 20 minutes into the flight, it has dropped below 30 psi, with an oil temp of only 170F - 180F.  (Start up pressure is about 50 psi).  After trying different gauges, we finally took the engine  off the airplane and took it back to Custom and witnessed it being hooked up on their test stand and showing the same numbers it had previously.  We took it back home, tried yet other gauges, (even two gauges at once, which both were within 1-2 psi of each other),  washering the relief valve, using different diameter oil lines from engine to gauge, verifying oil temperatures to be what the gauge showed, and finally took the engine back to Custom where they tore it down, re-checked all tolerances, put yet another Drake Aviation accessory case on it,  reassembled with new bearings, and put it on the test stand with again great numbers-----and again, when we put it on the airplane, it will still not hold more than 28 psi after the oil temp is stabilized at 180F---which means that come summer, it is really going to be lower. 

Idle oil pressure is about 9 psi with the 180F temp.  Differences in the test stand and on the airplane:  the test stand hooks the engine up to a dyno with a large flywheel, and a cooling shroud engulfs the top of the engine so the whole engine is nicely cooled, albeit the CHTs are at about 375F.   On the airplane, of course, we are driving a propeller, and behind the baffling, where the accessory case is, the cooling is going to be different.   Custom's stance at this point is that the engine is O.K., and we have an instrumentation problem---and I can certainly understand their position.  They have bent over backwards to try to help us.   However, we are pulling our hair out and running out of ideas.

Do you have any?

I personally know the guys at Custom, so I am sure that they did the best they could to check your engine.  I'm not sure if I have an answer as I would expect that the engine should continue to make pressure once installed in your airplane.

First, what kind of airplane is it installed in?  Homebuilts generally stir up weird problems like this.

Next, you went to a lot of trouble to check the oil pressure gauge- is the oil temperature gauge working?  Maybe the engine is running a lot hotter than you think and the oil pressure is dropping accordingly.

Other than that, I'm not quite sure what to tell you.  The oil pressure is not that far off of the mark as the normal range is 30-60 lbs, so your observed pressure is still within a couple of psi of the low limit.  There are lots of engines operating at much lower pressures than that! 

Harry

Follow-Up

To further play with our minds, here is the latest development with this oil pressure problem.  We wanted to install an automotive type oil pressure gauge (electric) and obtain a reading right at the case.  Well, there was not room to screw the sending unit directly into the case, so we installed an "L"  and then a "T", putting the sending unit into one leg and the same oil pressure line we've been using into the other, so we have now the automotive gauge and the Mitchell direct reading gauge both in the cockpit. In 4 hours' flying, with 4 different flights, both gauges show no less than 35 -36 psi at 2300 rpm with 190F oil temperature.    At full ground idle of 650 rpm and 180F, pressure is 12 - 14 psi.  The only change has been in the plumbing, EXCEPT, our ambient air temperature has dropped by about 15F since the last of the flights which revealed the lower pressures.  To compensate for that, I had closed off with metallic tape the 2" scat hose which cools the oil screen, thereby getting the 190F oil temperature. 

The next step will be to go back to our original set-up which we had when we first installed the engine and see what we've got.  I am "bum-fuzzled" on this, for sure.  I am wondering if the lower ambient temperature can somehow affect the expansion of the magnesium accessory case so that it is a little "tighter" around the oil pump, giving better efficiency.  I don't know how the oil temp of 190F (higher than we had previously) correlates with that. And, of course, none of this helps understand the difference between test stand figures and airplane figures. 

I have scrounged up an A-65 operators manual.  If you go to page 5, the spec page lists an oil pressure range from idle to rated power of 10 to 35 lbs psi.  You are reporting 9-28 psi with your engine.  Based on the information from the manual, it looks like your engine is operating pretty close to the manufacturer's specifications.

Regarding  the oil pump, the fit of the cover which goes over the gears and pump cavity is often a culprit with loss of oil prime or pressure.  The cover can warp or not fit flat to the top of the pump cavity, resulting in leaks at the mating surfaces.  You can check the fit by applying some machinists bluing dye to the mating surfaces and torque the plate down to get it seated.  Remove the plate and see if the dye spread evenly across the mating surfaces indicating an even fit.  You can lap the surfaces to even up any irregularities.  DO NOT apply any extra sealant between the surfaces. The sealant can dislodge, resulting in a sudden loss of oil pressure.

Another thing to check is the fit of the oil pickup tube where it screws into the accessory case.  As best you can, make sure that the tube is not leaking where the crush gasket seals the tube against the accessory case. Have you checked to make sure that the pickup tube does not have any obstructions?

I don't like to squint my eyes at a situation like this, but your numbers, while not perfect, are not too far out of the reasonable range.  This is an old engine, so maybe this is as good as it gets.

Harry

Pushrod-Tube Oil Leaks

I have an A-65 .  It has developed an oil leak that seems to be comming from a pushrod tube at the cylender head end.  How can I go about fixing it as it is causing a real mess in and outside of the cowling.

You need a special tool to fix the pushrod tube fit to the cylinder head. (see picture to right)


The tool fits into the end of the pushrod.  There are two ball bearings which are adjusted to put pressure on the inner wall of the pushrod tube.  When the tool is turned, the balls swage a tight bead between the pushrod tube and head.  This is pretty much the only way to fix this problem.

I bought my tool from D&S Cam Corp, www.dscams.com, for about $60.  Check with local mechanics to see if you can borrow one.  As they are in the business to fix things, they will probably want to bring the plane into the shop.  Most shop rates are about $60/hr, so the cost of the tool is not too bad in comparison.


Here is a picture of the area which needs to be swaged.  The tool has an inner screw which expands two opposing ball bearings into the surface of the tube.  Apply just enough pressure to tighten up the tube in the head and then turn the tool to compress a bead into the tube.  I’m pretty sure that D&S supplies instructions with the tool.  It is fairly self-explanatory, but when in doubt, consult a licensed mechanic.


Unless you are completely removing the pushrod tube, you don’t need to remove the cylinder.  If the tube needs to be replaced, then the cylinder will probably need to be pulled completely off.  The new tubes fit pretty tight and it is kind of difficult to fit them in with the cylinder just pulled forward off of the studs.  Of course, when the cylinder is pulled, the work becomes more complex because your will need the cylinder base nut wrenches and piston ring tools.

A piston ring tool can be bought at any auto parts store.  The automotive ring tool is like a steel band which compresses the rings down so the piston assembly can be slid into the cylinder.  The piston is installed into the cylinder before installing the piston onto the connecting rod.  Some of the automotive ring tools do not split open, so there is no way to remove the tool if the piston is connected to the rod.  I use a big band clamp (looks like a giant radiator clamp).  I am very, very careful about seating one ring at a time.  For sure, the band clamp is needed to seat the oil control ring at the bottom of the piston.  The piston pin is in between the compression rings and the oil control ring, so the connecting rod has to be attached with a spring compression tool in place.  The band clamp works well- simply unscrew it once the piston is inserted into the barrel.

However, I will stress that it is very, very likely for the novice to break at least one piston ring when doing their first install.  It is a clumsy job, and the oil control ring is especially vulnerable because they have thin edges and are more brittle than the compression rings.

You will need a 1/2” and 9/16” cylinder base nut wrench.  You can buy these from Aircraft Tool, www.aircraft-tool.com or US Tool, www.ustool-new.com.  When you get these tools you will find that some grinding of the OD and the height of the hex will be required to get them to fit.  Don’t grind too much as the tools are kind of low grade material and can break.

When you start to remove cylinders you will find that there are through studs which connect cylinders on both sides of the case.  You’ll sort this out pretty quick when you are turning a nut which never seems to get loose.  Use a regular wrench to hold the opposite nut on the through stud.

The cylinder will be required to be pulled off of the studs by 2” or so to provide clearance to remove the pushrod.  Getting the tube out is the easy part.  The new tube will be a tight fit and you will find it a bit awkward to tap in the new tube with the cylinder hanging on the engine.  I’ve never installed a pushrod tube with the cylinder installed on the engine, so I don’t know how hard it is to do it this way.

Be careful when the cylinder is hanging from the connecting rod to make sure that the rod does not clatter up and down in the cylinder bore in the case.  The rod can gouge the bore surface which will result in oil leaks.

Harry

(RJW Note:   Harry feels that the above operation takes a bit of experience, and does NOT recommend that people with no expertise tackle it on their own.  I've successfully removed and replaced a cylinder on my own engine, but personally wouldn't tackle trying to swage the pushrod tubes.  Harry also points out that the procedure is way, way above what the FAA allows under "owner maintenance" for certified airplanes.)

Follow-Up

What else should I look for...e.g. what has caused the problem in the first place or another reason why I have the oil leak?

I could write for a month on engine oil leaks.  Every mating surface on the engine is a potential source for an oil leak, let’s not kid ourselves.  Unless your engine was overhauled yesterday, it is realistic to expect that it is going to seep oil.  This isn’t to say that the engine can’t be made to be relatively dry and free of major oil leaks, but calendar time increases the likelihood of leaks.

Loose pushrod tubes are common.  The fit of these tubes into the head is not scientific.  There is no spec on fit, it is literally a TFAR installation (That Feels About Right).  The swage should not be overdone so that the bead cuts too deeply into the tube so as to cause a stress crack, but should be held firm with light tugging.  No movement between the tube and the head should be allowed.  Sometimes the tubes spilt, but they do leak at the install point frequently, so it is safe to assume that the tube is loose.  If the tube splits, the oil spray is really messy.  If it leaks at the head, there will be a dirty oil pattern on the back of the head where the tube is leaking.

As far as why these parts leak, once again, it is pretty basic.  The friction fit of the tube to the head just loosens over time or with jostling of the cylinder during install.  I’m don’t think that the tubes can be replaced with the cylinder installed on the engine.  I have only installed new tubes with the cylinder on the bench.

Another common source of oil leaks is at the rubber boots which connect the pushrod tube to the crankcase.  It is common for the circular ring closest to the engine case to not align in the groove in the rubber boot during install.  The ring will kind of sit along the rear ridge of the groove and oil will seep out.  A leak at this point can be detected by looking for a bubble of oil on the bottom of the retaining ring or boot.  I orient the rings so that the end tangs are pointing down, which makes it easier for on oil bubble to form and therefore make leaks easier to detect.

However, if the engine is leaking from other points, like the top case, the cylinder to case mating surfaces, or through studs, the oil will collect on the little rubber boots, providing a false indication.

Otherwise, any leak on the engine can make the inner cowling messy.  There is a lot of air swirling around, and a little bit of oil goes a long way to making a big mess.

Harry

Oversized Pistons in Non-Oversized Holes

Harry, I need your expertise once again. I am an IA doing an overhaul on my own A-65. When I measured the cylinder bores they were a little worn but within the standard limits as per overhaul manual . The problem is that the pistons are marked with M10 on the top of them and when I measured the piston to cylinder fit it was only .007. The Overhaul manual says it should be .014 to .019.

Do you think that someone over the years has put M10 piston in standard cylinders. Please Help! I am scratching my head!.

Well, the simple answer is that someone installed .010 oversize pistons in your cylinders.  Your measurement of .007 clearly indicates that the fit of the piston to cylinder wall is .010 too tight- a standard piston would fit about .017 and yours, with the M10 piston, is at .007.

Who knows why the wrong piston is installed in your engine?  Was this a homebrewed performance mod with cut down rings?  Was it simply a mistake?  Maybe your engine was robbed of parts and slapped back together with whatever was lying around. My opinion is that logbooks don’t really give the true story of an engine’s condition.  The condition of the engine can only be determined by a hands-on inspection.
 
Frankly, nothing surprises me at this point.  The engine which was installed in the A-65 in my Champ was overhauled in 1963 and ran until 1999 for about 1200 hours without being opened up.  It ran like a fine watch, and I only tore it down because every gasket had gone bad and the engine leaked oil from every connection.  When I tore it down, I found that the crank had been ground .010 under and standard bearings were installed!  I could not believe that it would even make oil pressure, but it did with no trouble.  The crank hammered around so much that all of the bearing webs in the case were cracked.  The case also had spiderwebs of cracks radiating from every cylinder hold down stud.  Despite all of the problems, this engine really ran well.

I have dozens and dozens of stories just like this.  I could write volumes on how engines are built wrong.  What boggles my mind is how well many aircraft engines run, despite having been built up wrong.

Harry

Finding Parts

We are a small group of British enthusiasts who own a Jodel 112. Recently we replaced its A65 8F which was suffering from low oil pressure with a healthy A65 8F and would like to refurbish the original engine. The cause of the low oil pressure has been identified as catastrophic failure of the oil pump bearing which destroyed the rear casing and gears, which damaged the main bearings due to a lack of pressure and metal debris.

We have sourced a new rear casing and associated pump bearing and gears and have a shop which can take the mains down to -.020 (it needs grinding) and was already down to and fitted with -.010 bearing shells.

We can't source any -.020 bearing shells any ideas?

Also we are looking for a few spare Cylinders but understand that Millennium our preferred option are no longer trading.

Are there any other options that you would recommend of do you know of stock of Millenniums anywhere?

Contact Aircraft Specialties at 918-836-6872, or find more contacts at  www.aircraft-specialties.com.  The last time I bought a set of .020 bearings the price was about US$350.  Don’t have an automotive shop grind the crank because the radius at the ends of the bearing journal are different slopes between automotive and aviation applications.

Superior is the only source for new cylinders and their supply of late (Nov 2008) has been sporadic.  Superior is a separate company, but owned by Thielert, and is being affected by the bankruptcy of the Thielert engine side of the company.  For cylinder spares, contact Aircraft Specialties, Edgecumbe G&N www.edgecumbegn.com, or AERO at www.aeroinstock.com.  However, I think that you will find that Superior cylinder kits are in short supply at the moment.  There is a fellow by the name of Woody Herman who has a large supply of disassembled A-65 engines.  I can’t find a local number, but his 800 number is 800-279-3168.   I know that this doesn’t do you much good from England, but I will give him a call to get a better contact.

Harry

Generator Removal Problems

I may have missed it, but is there an easy way to get to the top nut on the generator attachment on the O-200?

Having done this many times, I will just cut to the chase.  If you are working on a Cessna 150, remove the top and bottom cowling for maximum clearance.  Next, remove the left magneto as this is the easiest path to get to that nut.  If you don’t remove the magneto you will spend hours trying to figure out how to get a wrench on that nut.  Once that left magneto and all of the cowling is off, it is easily 30 minutes or less to get the generator off.

You can try to take off the tach drive housing, but you will still have a challenging geometry to get a wrench on that generator nut in the 11 o’clock position.  Also, it is likely that the gasket will start to leak under the housing once you remove it.

Probably not the answer you want as timing the magneto seems to intimidate some people.  However, if you total up the overall frustration level of taking another path, it is much easier to remove the mag to access the nut.

Harry

[RJW Note:  I'll echo Harry's advice.  I tried and tried to take off my generator without removing the left mag, but just couldn't manage it.]

Determining What Parts are Installed

I have become involved with a Continental C85-12F that I suspect has an undocumented O-200 crankshaft. The propeller flange has a square edge, not a beveled edge like a C85-12 F or an A65-8F. The logbooks were conveniently lost when the engine was installed on an Aeronca Champ in 1995. The owner has purchased the Aircraft Specialties STC to attempt to legitimize this engine. It has fallen on me to determine if the installed parts are in compliance with the STC. Is it possible to determine if the O-200 rods and pistons are installed without a teardown?? I have verified the C85 camshaft by measuring the valve lift. Is it possible to determine part numbers without a complete teardown?? The engine is running well and it is a shame to tear it apart if there is another way. 

To get right to the point, there is no way to identify the internal parts without accessing the internals.  At the minimum, at least one cylinder and probably two from the same side will need to be pulled off of the studs a few inches to view the connecting rods and the backside of the pistons.  Position the piston to the Top Dead Center position, and pull the cylinder outward, but don't pull the piston out of the cylinder.  If you have a helper hold the cylinder, you can get enough of a view into the engine to see the back of the pistons either by eye or by using a mirror.  The same goes for the rods- you can easily see the rods with the cylinder pulled off of the studs, but not completely removed.

Finding a part number on the rods may or may not be a problem.  Newer manufacture rods have the number etched on the rod frame whereas the older rods have no numbers except for a casting number embossed on the rod neck.  Identifying the O-200 rod is then done by visual inspection if a part number cannot be verified.  The C-85 and O-200 crank have the same pin to pin distance from the wrist pin to the crank journal, but he mold line down the center of the rod and the width of the rod at the piston pin journal is different.  The C-85 has a wider piston pin journal than the O-200.

The part number of the piston may be cast into the backside of the piston head where the piston pin is attached.  But, some pistons have simply used an ink stamp for a part number, which becomes obscured or erased once the engine has been assembled and ran.  Somewhat good news is that the C-85 and O-200 piston are physically different, so the visual identification is easy.  The bad news is that at least one cylinder will need to be completely removed to expose the piston.

From my perspective, the job which you are describing is actually not all that hard and not too invasive to the engine.  Really, it amounts to pulling a cylinder or two from one side of the engine.  For an experienced guy with all of the right tools, this is a two hour job.  For the first timer, it might take most of a day, or maybe a weekend of tinkering around.

Harry

Adding an Electrical System

I am looking at an Aeronca 11B/C Conversion with a C-85-12 engine.  I recognize that the -12 case has the plates covering the openings for a starter and alternator, but this aircraft obviously is void of any electrical system.  What is involved in adding a very simple electrical system and what's the approximate cost involved?  I would like to get away from hand propping the aircraft, but don't want to add a lot of
weight or expense.

There are two aspects to consider to your question.  First, adding the starter and generator to the engine is simple- just bolt the parts on.  But, the airframe will require some sort of wiring, voltage regulator, battery, battery box, switches and the all important FAA approval.  Adding an electrical system is not terribly hard, but it is certainly not an afternoon project.

If you buy a new lightweight starter and an overhauled alternator the cost will run about $2200, plus labor.  A new starter is about $550, alternator about $750, battery about $140, battery box about $85, voltage regulator $150, and assorted cables, wiring, breakers and switches will eat up $500. I would estimate that it will take about 20-30 hours for the installation at shop rates.  At $50/hour that runs about $1000 to $1500 just for labor.  So, at the top end, you are looking at $3200 to $3700 for all of the work. (2008 prices)

Of course, scrounging up serviceable, used parts will affect the overall cost.  Even with used parts, it would be reasonable to expect to pay $750 to $1000, plus labor.  You might be able to do the work, but a licensed FAA mechanic with Inspection Authorization is going to have to approve the installation.  I don't think that you will need an STC, but the installation will have to be done in accordance to some configuration found in the Aeronca Type Certificate Data Sheet.  The National Aeronca Association or the Fearless Aeronca Aviators can help with the install data.

There will be a weight penalty, also.  Expect to add 45-60 lbs to the airframe, depending upon the exact weight of the parts used.

Realistically, there is no way to get away from hand propping or add an electrical system without some amount of expense and a fair amount of added weight.

Harry

Prop Strike/Not-a-Prop Strike?

I have a chance to buy an 0-200 that is coming from an accident plane.  I know the prop strike/sudden stop issue has been brought up before, but this one is a little different, and I was hoping for your input.

The engine failed in flight due to fuel starvation.  Just prior to impact with the trees, the pilot slowed the plane up to near stall speed, and noted the prop was NOT turning.   However, as it crashed through the trees, one propeller blade took a big hit, and bent that blade back nearly 90 degrees.  The engine still seems to pull through smoothly

Does that meet the definition of sudden stoppage?  Since the engine wasn’t rotating, part of me says it was not, but part of me thinks it could be even worse.   We haven’t dialed the crank yet, or done anything else to the engine, except pulling it through. 

The engine has about 1300SMOH (Overhaul  about 12-15 years or so) and had a couple jugs replaced in the last 300 hours.  Good compression on all four cylinders, not drinking oil, seems to be healthy prior to crash.

The bottom line answer from TCM is defined in Service Bulletin SB96-11B.  Here is the link to that Bulletin:  http://www.tcmlink.com/pdf2/SB96-11B.pdf

Straight to the point, T.C.M.'s Service Bulletin 96-11 states that if a propeller must be removed from the aircraft to be repaired following a propeller blade impact of any sort or if the engine physically lost R.P.M.'s from the incident, then the engine has experienced a propeller strike and it should be removed from service and completely disassembled and thoroughly inspected for damage from the incident.

This situation is a no-brainer.  The force required to bend that propeller 90 degrees backwards was substantial, and the risk of bearings being shifted or cracks at the inner bearing journals is substantial.  For the cost of a gasket set, there is no question that a teardown should be accomplished.

Harry

Identifying Internals without a Teardown

Hello Mr. Fenton, I have become involved with a Continental C85-12F that I suspect has an undocumented O-200 crankshaft. The propeller flange has a square edge, not a beveled edge like a C85-12 F or an A65-8F. The logbooks were conveniently lost when the engine was installed on an Aeronca Champ in 1995. The owner has purchased the Aircraft Specialties STC to attempt to legitimize this engine. It has fallen on me to determine if the installed parts are in compliance with the STC. Is it possible to determine if the O-200 rods and pistons are installed without a teardown?? I have verified the C85 camshaft by measuring the valve lift. Is it possible to determine part numbers without a complete teardown?? The engine is running well and it is a shame to tear it apart if there is another way.

To get right to the point, there is no way to identify the internal parts without accessing the internals.  At the minimum, at least one cylinder and probably two from the same side will need to be pulled off of the studs a few inches to view the connecting rods and the backside of the pistons.  Position the piston to the Top Dead Center position, and pull the cylinder outward, but don't pull the piston out of the cylinder.  If you have a helper hold the cylinder, you can get enough of a view into the engine to see the back of the pistons either by eye or by using a mirror.  The same goes for the rods- you can easily see the rods with the cylinder pulled off of the studs, but not completely removed.

Finding a part number on the rods may or may not be a problem.  Newer manufacture rods have the number etched on the rod frame whereas the older rods have no numbers except for a casting number embossed on the rod neck.  Identifying the O-200 rod is then done by visual inspection if a part number cannot be verified.  The C-85 and O-200 crank have the same pin to pin distance from the wrist pin to the crank journal, but he mold line down the center of the rod and the width of the rod at the piston pin journal is different.  The C-85 has a wider piston pin journal than the O-200.

The part number of the piston may be cast into the backside of the piston head where the piston pin is attached.  But, some pistons have simply used an ink stamp for a part number, which becomes obscured or erased once the engine has been assembled and ran.  Somewhat good news is that the C-85 and O-200 piston are physically different, so the visual identification is easy.  The bad news is that at least one cylinder will need to be completely removed to expose the piston.

From my perspective, the job which you are describing is actually not all that hard and not too invasive to the engine.  Really, it amounts to pulling a cylinder or two from one side of the engine.  For an experienced guy with all of the right tools, this is a two hour job.  For the first timer, it might take most of a day, or maybe a weekend of tinkering around.

I've attached a couple of pictures, and while not the best quality, you will get the idea.


The casting number for both the C-85 and O-200 rods is Atlas 5561 and is the only number visible on most rods.  The O-200 rod is narrower at the piston pin end, 1.13" vs 1.37" for the C-85 rod.  Another identifying feature is that the O-200 rod has a flat spot machined in the crank journal cap end where the oil squirt hole is located.  Other than that, the O-200 and C-85 rod share the same casting blank.

Harry

Black Flecks in the Oil

While cleaning my oil screen in my Continental A75-8F, I noticed some black flecks on the screen and at the based of the threads in the engine where the screen screws back in.  I cleaned out two finger tip coverings just below the threads.  They appeared to be coagulated or baked pieces.  However, a magnet did pick up some of them.

I recently started using the gold label, SAE-50 anti-ash, dispersant, with an additive for improved lubrication (AeroShell) and don't know if this had something to do with it or if there's a potential problem with the engine.  Thanks for any advice.

Lots of missing details on your engine such as hours, airframe application, etc.  However, let me take a swag at an answer. 

You mention a change to Ashless Dispersant oil, or AD oil.  This type of oil is nicknamed “Detergent” oil because, loosely speaking, it has chemical qualities which clean carbon and other deposits from the engine and suspend them in the oil.  Contaminants too big to be suspended in the oil are trapped in the filter, or in the case of your engine, the screen.  After engine overhaul, it is common to use what is referred to as mineral oil or “Non Detergent” oil for break-in.  The discussion over why mineral oil is used at break-in has consumed volumes of writing, but it more or less boils down to that the additives in detergent oil may inhibit the friction required to get the rings to seat properly in the cylinder barrels.  After a period of initial operation, the break-in oil is typically replaced with detergent oil because of the “cleaning” qualities and other lubrication benefits of this type of oil.

During initial break-in, the piston rings don’t seal very well for the first few hours of operation so oil makes its way into the combustion chamber or is turned into carbon where the rings leak.  During this process, some carbon may be pumped past the rings into the engine during the combustion process.  This carbon eventually makes its way to the filter.  Likewise, during break-in, a lot  of metal parts are scraping around, knocking off the high points of the metal to metal contact.  These small bits also find their way into the oil and, if large enough, get trapped by the filter or screen.  In fact, as all of the parts wear over the operational life of the engine, the worn metal from all of the moving parts eventually finds its way into the oil system.  For the most part, but not always, the worn metal components will be undetected in the screen or filter.  But not always…

 The black flecks which you describe sound like normal carbon bits, and the detergent oil probably loosened deposits in your engine.  The small metal bits may have been embedded in the carbon, which is why some of the black bits appeared magnetic.  The normal course of action would be to assess if the material in the screen is excessive, or of a small enough amount to continue the engine in service, and pull the screen after a few hours to see if the problem re-occurs or worsens.  Chances are that the next screen inspection will yield a clean screen.  The detergent oil probably just loosened ups some sludge in the engine.

If the carbon continues, then this could be an indicator of a problem with the rings sealing in a cylinder.  The rings, don’t seal, the combustion blows by the rings and cooks the oil, resulting in carbon.  A broken ring would also contribute to an increased metallic content in the oil and oil screen.  Another possibility would be a cylinder with a rusty bore.  If the bore rusts, the rings don’t seal and also scrape the metallic rust, which results in an  increased metallic content into the oil.  It is not uncommon for large rust patches to develop in steel bore cylinders, especially on engines operated in the humid south or northern engines equipped with engine pre-heaters.  If an engine is fitted with an electric block heater,  and left plugged in continuously, the internal temperatures may cross the dew point and condensation will occur and rust the engine internals.  Another northern problem is low oil temperatures.  Oil is hydroscopic, and chemically attracts water.  If the oil does not get hot enough, then the water does not boil out of the engine and can condense and cause rust.  It is extremely common after a flight on a 30F day to see water dribbling out of the breather tube or a caramel colored foam (water/oil discharge) at the breather outlet.

 So, going back around in a big circle to answer your question, the black flecks are most likely carbon, and probably dislodged from the engine by the detergent oil.  The reasonable action would be to run the engine no more than 25 hours and then check the screen for contaminants.  You can check the screen at any time, but it would be best the run the engine about the same number of hours it took for the current crop of carbon to accumulate.  If you run a similar range of hours between oil changes, then you will have some sort of side to side comparison to work from which to evaluate if the situation is better or worse.  From what you described the original amount of contaminants was enough to raise an eyebrow, but not enough, at this point, to cause concern that the engine was failing.  However, I have not been able to physically view your engines, so my diagnosis is based upon a couple of lines of description in an e-mail.  Get a mechanic to look at your engine to make the correct call.

Harry

Converting a C-85 to a C-75

Are there any provisions to take  C-85 to a C-75 since the application that I'm using it on requires a C-75-12.

Here is a statement out of C75/85 Type Certificate Data Sheet, Note 4:   “The C85 series engines are similar to the corresponding C75 series except for rating and a different carburetor setting.”  The C-75 also has a max continuous rpm of 2275 vs the C85 at 2575 rpm.

However, according to the Teledyne Continental Parts and Overhaul manual for this engine, Marvel Schebler lists one model and part number of carburetor for both engines:  MA-3SPA, p/n 10-4240.  The manual also lists two different Stromberg carburetors:  380162 for the C75 and 380167 for the C85.  The primary difference between the two is that the C75 requires a 1-5/16 venturi and #46 main metering jet, whereas the C85 requires a 1-3/8” venturi and a #45 metering jet.  Refer to table XIII in the Overhaul manual for specifications.

If this is a Type Certificated application, you will require some FAA approval for this modification because the data plate and part numbers will need to be altered.  I’m not aware of any Service Bulletins or factory approval for these changes.  You will have to document the changes using information from the Type Certificate data sheets and Overhaul Manual which detail the similarities and differences, and then submit an FAA Form 337 Major Repair and Alteration.  This will require a mechanic with an Inspection Authorization to prepare and handle the submittal to the FAA.

If this engine is to be used on an experimental application, I would probably just run the engine at 2275 rpm instead of 2575 rpm and see how it works.  Given that Marvel Schebler uses one p/n of carburetor from the C75 through C85, I suspect that the engine hp rating is more related to the rpm limits than anything else.

Harry

Official TBO

Hello, Can you please tell me the time before a major overhaul on a A65 engine? I'm a rookie aircraft owner and am trying to know what I'm talking about when someone asks me a question about my Aeronca Chief.

Continental Service Information Letter SIL98-9A provides details on engine TBO times.  Here is a link:  http://www.tcmlink.com/pdf2/SIL98-9A.pdf

The TBO for the A-65 is listed as 1800 hours or twelve calendar years.  TCM makes a distinction between hours and calendar time as some engines can go three or four decades before accumulating enough hours to warrant an overhaul.  The biggest problem over time is simply the degradation of gaskets and corrosion.

In reality, for an airplane operated under FAR 91 (generally speaking, the FAR which applies privately owned aircraft) the engine manufacturer’s TBO is simply a recommendation, not a requirement.  The engine can be run indefinitely and airworthiness is determined by the mechanic at each annual inspection.  Ultimately, the engine will start to degrade either by loss of oil pressure or compression and an overhaul will need to be accomplished.

Speaking of Aeroncas, there are a couple of great Aeronca groups on the web.  The Fearless Aeronca Aviators, or FAA list, and the National Aeronca Association, www.aeroncapilots.com.  Also, check out Todd Trainor’s Aeronca site at www. Aeronca.com.

Harry

A-50 Engines

I found your wonderful web site by a search for Continental a50 and GPU, it has been questioned if this engine was aircraft or GPU. I have attached photos and would be interested in any information you could add.

I am 68 years old and planning to make a major downsizing. So this engine will have to find a new home.

I believe the mag is Bong single ignition. I have this from memory, I can't find any reference to bong on the web. What is left of the exhaust appears to be exhaust up. You can read the /Marvel Schebler /carburetor in the attached photos.

Unfortunately the information plate is missing. It looks to me like a dry sump oil system. Possibly an A50-1.

I found the engine outdoors some years ago. I have stored it in a dry garage since I have owned it. I believe I turned the crankshaft a little in the
past to see if it was free, but today in the cold I could not turn it.

I like the cast valve covers, I think they look sharp compared to the pressed steel ones on an A65.

The pictures of the attached engine show a very early A-50-1.  The dry sump and up exhaust configuration are unique to this engine.  The carb and the Eismann magneto are not original, but probably worked well enough.  The Marvel Schebler carburetor is probably from a 65 hp Lycoming which would match the A-50 performance.

If I had to guess, this engine was probably used on an ice boat.  The oil tank is not an aviation part, and the other parts not specific to the A-50 indicate that it has been pieced together.

Value-wise, this engine probably is not worth more than a few hundred dollars.  The A-50 was not used on many airplanes, and the airplanes which did use the A-50 were quickly upgraded to the A-65 because 15 more horsepower was a real performance increase.  Most A-50 powered airplanes were really underpowered as the A-65 usually is just kind of adequate. Another issue is that a lot of the major parts of the A-50 are different than the A-65- crankcase, cylinders, pistons, etc.  Of course, this engine sat outside for quite some time and there are no log books.  You may find a collector who wants to preserve an old engine like this, though.  I have not seen very many (if any) A-50 engines in museums or in airplanes.

Harry

A65 Internal Case Color

What is the red on the inside of the A 65 engine crankcase?

I have observed that the A-65 engine cases, primarily from the 40's vintage, were painted or dyed red on the interior surfaces.  I am not sure exactly why, but I do know that this was the practice for a number of years.  I have several cases which clearly show the red interior, but the finish does not appear to be paint, but maybe some other type of coating.  From the practical standpoint, it would seem paint would not make a lot of sense as it would flake off and block oil galleys.  A machinists dye or anodizing would make more sense as it would gradually wear away and not obstruct oil passages.  The finishes I have seen seem to support the second type of finish.

I've often wondered why the case internals were painted red.  Was it a method to track machining processes?  Was it a method to improve oil drain back by reducing the oil sticking to the internal surfaces?  Was it a marketing gimmick connected to the old Red Seal marketing of the Continental engines?

Harry

Breaking the Glaze with Bon Ami

Recently, I've helped a friend with his engine on his wag aero cub ( C-85) . Anyways the engine was in bad shape, and I majored it, and put on a set of NOS chrome cylinders that a friend had given me a few years back, The long and short is I cant get the rings to seat! I've pulled the cylinders, honed them, and then re installed everything with new rings (from Fresno air parts- no chrome rings, only steel and cast) and still no joy..

My question is regarding Bon Ami, I remember years ago my uncle pouring Bon Ami Cleaner into snowmobiles to help the rings seat, and I'm wondering if this will work with the chrome cylinders on an aircraft engine. My friend is not made of money, so he wants to try everything to get these to work, before buying a new set of jugs.

Straight to the point, don’t pour Bon Ami, or any other abrasive, into an aircraft engine cylinder in order to break it in!  This might be ok for a snowmobiles or lawnmowers, but proper mechanical honing is the only way to break the glaze on an aircraft cylinder.  I don’t think I have to explain why introducing an abrasive powder into an aircraft engine is a bad thing…

Usually, it is not necessary to hone a chrome bore cylinder, although it probably can’t hurt to lightly hone to break any glaze on the surface.  The purpose of the honed surface is to create peaks and valleys which retain oil to lubricated the contact surface between the rings and the cylinder wall.   Chromed barrels are actually referred to as “channel chrome” and if you look at the chrome surface, you will see cracks, or channels, which serve as reservoirs for oil to keep the ring to barrel surface lubricated.  So, by design, the chrome surface of the barrel should be shiny and slick, and the cracks and channels should act in the same manner as the honed cross-hatch in a plain steel barrel to retain lubricating oil.

Regarding break-in, chrome cylinders are notorious for these kinds of problems and easily take twice as long to break in as plain steel cylinders, maybe as much as 50-100 hours before oil consumption stabilizes.  A quirk of chrome cylinders is that the chrome surface has a higher friction value than plain steel cylinders, so the heat generated by the break in process can anneal, or soften, the cast iron ring should the cylinder run too hot. On the other hand, if the chrome cylinder is not run hard enough, the surface of the cast iron ring can be polished which  will result in high oil consumption.  Run chrome cylinders hard, but don’t overheat them.

Don’t baby an engine with chrome jugs during break-in, run it at 75% power or higher during the initial 5-10 hours of operation.  Do not perform extended ground runs as the cooling will be inadequate and will certainly glaze the cylinders within as little as 20-30 minutes of running.  The test cells used by the OEM’s and quality engine rebuilders use a huge fan to duct air over the top of the cylinders during engine test cell runs.  The airflow generated by an aircraft in flight is ample to cool the engine

Another consideration may be the pistons.  If new pistons were not installed at overhaul, then this could be a contributing factor.  The ring lands wear on used pistons and the ring may lack enough support to provide outward sealing tension between the piston and cylinder wall.  Worn lands may also allow the ring to “walk” or twist up and down in the land, which also prevents a solid seal. This is a very common problem as a used piston may be cleaned up to visually look new, but the ring lands may be worn beyond limits.

There are literally dozens of articles and support information on cylinder break-in to be found on the web.  Here are just a few links:

http://www.avweb.com/news/maint/184932-1.html


http://www.shell.com/home/content/aviation-en/aeroshell_site/technical_articles/techartpages/techart08_30071255.html

http://www.eci.aero/pdf/88-7-1.pdf


http://www.aircraftcylinders.com/CylinderPlating101.html


http://www.aircraftcylinders.com/BreakInProcedures.html

Harry


I'm building a 0-200 for a Midget Mustang and had a question about cylinders. I purchased four cylinders off a 0-300 that all had 74 and higher compression, they have about 700 hours on them. When I received them they look fine but have a fair amount of a light tan buildup in the cylinder head and piston tops. My question is should I try to remove all this buildup or just run them since they were running good when removed? If  you think I should clean them up what is the best way to do that? Thank you for your help and thanks' for all the wonderful information you provide to us on your website.

There is also an argument to be made for re-assembling as is.  If the parts were running when disassembled, then they should run assembled.  On the other hand, there is a fundamental "neatness" to cleaning the parts on an engine to be assembled.

Combustion deposits can be pretty tough to remove, though.  Engine shops will bead blast with glass beads and very, very carefully clean up the blast material with a lot of air.  Just a few beads will really cause a lot of scoring or even failure.  The cylinder can be a real problem because the valves really should be removed if it is bead blasted.  There are no shortcuts- expect to use a lot of elbow grease to loosen and scrape the deposits off.  You can used just about any scraping tool, just don't score the material surface.  Tapping on the crusted material helps to break it away.  Sometimes soaking in Lacquer thinner or MEK will help to loosen the deposits.  Screw a couple of spark plugs into the cylinder, invert it and pour some lacquer thinner in the head and let it sit.

Or, clean up as best you can and re-assemble as is.

Harry

C-85 Cylinders in A65 Case and Case Reinforcement

 I have been reading your web site for years and passing it on to other Continental friends every chance I get.  I have used a lot of your ideas and gained a lot of information from it. 

I do have several questions as I am in process of putting together a bunch of parts as my original A65 cylinders were worn so much they couldn’t be cleaned up at .015 O.S..  They are no good.  I have some C85 cylinders in specs so plan on putting them on the A65 case. 

You mention re-enforcing the case.  (Yes there is a crack opposite # 3 cylinder)  Is the re-enforcement only in the 2 holes ( about 1” x 1 ½ “) in the center web? 

Also do you or anyone else know the aluminum alloy the cases are made of, as we have all kinds of heat treating outfits around and I am sure they will want to know?  What material is the specs for stress relieving? 

Also I take it that thread is no longer used between crank cases as a seal.  The engine will be broken in in a J3 type aircraft with 72” x 46 wood prop.  Then put in a KR2 with a metal 69 “ x 50 prop.
  • Case is C-65—8 #5467068
  • A65 – C85 crank
  • C-85 cylinders + .015 O.S.
  • C-85 lifters and push rods
  • C-85 cam

Here is a link to an field approved modification to install C-85 cylinders on an A-65 case:

http://www.popularaviation.com/337/8.pdf

Follow this link, and then scroll to page 10 for a description of case mods for the C-85.

http://www.if1airracing.com/library/IF1%20Technical%20Rules%203-14-07.pdf

 I am not sure of the case alloy, so you will have to kind of work from the recommendations of the heat treating outfit.  Obviously, the PFA may be of some help (maybe not).

Silk thread may still be used for a seal between the cases.  Most engine shops still use the thread to seal case halves.  Here is a Continental Service Bulletin on this topic- skip ahead to page 10 and read on:  http://www.tcmlink.com/pdf2/SIL99-2B.pdf

It sounds like you are planning to break this engine in on the ground- be careful as running the engine on the ground for too long can lead to glazed cylinders.  You should run the engine on the ground just long enough to get the idle and full throttle stops set, and to verify oil pressure settings.  You want to confirm that the engine is safe to operate, but the real break-in should occur in-flight  Here is a Continental Service Bulletin on this topic:

http://www.tcmlink.com/pdf2/M89-7R1.pdf

 Harry

Severe Stromberg Leakage

I have a new ercoupe with a Stromberg carb. when the plane was delivered, the pilot ran out of fuel. Now, in the shop, we are looking for the fuel leak. So far, no luck. However, the A&P pressurized the fuel system, and now my carb leaks, and the engine runs so rich it smokes and runs very rough. Is taking the carb off, and rebuilding it the best solution? I know nothing about Strombergs.

How did your mechanic pressurize the fuel system?  Was there fuel in the system or did he just apply air?  A sure way to wreck the carb is to blow compressed air up through the intake side to pull fuel out of the venturi.  Shop air has too much velocity and can actually create a negative vacuum in the float chamber.  This negative pressure can implode and crush the brass float.  If the float implodes, it won’t float, the needle valve which controls fuel flow to the bowl will stay open and the carb will run exactly as you describe.  The only way to diagnose the carb is to take it off and send it to an accessory shop.  I highly recommend Aircraft Systems in Rockford, IL, 815-399-0225.

Make sure that the primer isn’t leaking.  Extra fuel can be pulled through the primer and the engine will run rough primarily at idle.  Usually, the small amount of fuel from the primer doesn’t cause much of a problem at cruise or takeoff rpm.

A leaking intake valve could be a problem, but this is very easily picked up on a compression check.  Apply 80 psi of air and listen for air blowing back through the intake.

You mention that the pilot ran out of fuel.  Did he run low, or run out to the point where the engine stopped?  If he used too much fuel, as in something in excess of 8 gallons/hr, then the plane was either leaking it out of the vent system or it was getting siphoned past a leaking gas cap.  Check to make sure that the fuel pump diaphragm hasn’t ruptured.  If the diaphragm ruptures, then fuel is pumped overboard or back to the tank via a relief tube.  I would think that the engine would have run exceptionally poor had it been losing a lot of fuel through the carb.

I’m not sure if this helps, but here is a link to some info on the Ercoupe fuel system:  http://www.ercoupe.net/ads/55_22_02.html

Harry

[Also, there's lots of information on Stromberg carbs on the Engines Page under "Technical Help" - RJW]

Oil Screen Gaskets

Where can I get the crush washers for the oil screen on my A65-8.  It's is near time to change the oil.

You will need two gaskets- the one that goes beneath the nut which attaches the oil temp probe to the oil screen housing (AN900-10) and the gasket which goes between the oil screen housing and the accessory case (AN900-28).  When installing the gasket, there is a solid copper side, and a side with a split where the copper folds around the inner gasket material.  Fit the solid copper side against the accessory case and against the oil screen housing.  In other words, the solid copper side should face forward, towards the propeller end of the engine.

Aircraft Spruce stocks these gaskets.

Harry

C-90 Camshaft Replacement

I am rebuilding a 1960 experimental "Emeraude" in France. The plane has a Continental C90-12F manufactured in 1953 that is in a very good shape. I would like to replace its camshaft for a O-200 camshaft in order to have a little more power. I am also planning to fit that engine with E-mag electronic ignition system.

Would you mind comfirming that it can be done ?

Also, can I keep the C90-12F camshaft gear (P/N 3506 or 530535)  and put it on the O 200 camshaft ?

And finally, which is the part number for the mechenical fuel pump that goes with that O 200 camshaft ?

Following this short explanation, I have attached a comprehensive description of camshaft styles and part numbers so that you can understand what will fit your C-90 engine

Changing  the camshaft is more complicated than it seems.  The C-90 used either cast iron or steel camshafts, depending upon the part number of the camshaft.   The O-200 is a steel camshaft.  The lifter bodies must be matched to the material of the camshaft, so the changing to the O-200 cam may  require new tappet bodies if your existing camshaft is cast iron.  If you don’t get the correct tappet bodies matched together, then the camshaft and tappet bodies can fail rapidly.  The document below provides dimensions of the tappet face to determine if the tappet is steel or cast iron.

The  C-90 cam may actually provide more performance than the O-200 cam, also.  The early C-90 camshafts were designed to provide power with wooden propellers, so the camshaft lobe profile is a bit better for making power with a little less efficient propeller.  The differences between the later C-90 and O-200 camshafts are probably so slight as to not be noticed.

The real difference in power between the C-90 and the O-200  is simply rpm.  The C-90 is rated at 2475 rpm and the O-200 is rated at 2750 rpm.  The reciprocating parts of the C-90 and O-200 are virtually identical, so just run the C-90 at 2750 rpm to make more power.  This can be accomplished with no engine modifications, just pitch the propeller to turn more rpm.

If you do decide to change the camshaft, the camshaft gear is the same between the C-90 and O-200.  The fuel pump is part number 40585 and is approved on all C-75 through O-200 engines.

Here is some additional info on the C-90 cam: http://www.aeronca.org/ContinentalSB-M49-17.pdf

Here are the power curves on Continental engines from the A-65 through O-200:  http://www.popularaviation.com/docs/ContinentalPowerCurves.pdf

Also, there is a very lengthy set of discussion to be found about the C-90/O-200 engine at www.SuperCub.org.  You will need to use the search engine within the website, but look for PA-11 engine or engine mods.


Harry

Parts description


 
SECTION 4:  CAMSHAFTS, VALVE LIFTERS, & PUSHRODS

CAMSHAFTS:

A series:
4546

C series:
40584 - cast iron (C75, C85 - side fuel pump or none)
24652 - cast iron (C75, C85 - fuel injector drive)
24435 - cast iron (C85-12, C85-12F - dual fuel pump drive)
530788 - steel     (C90 - carburetor only - side fuel pump or none - replaced by 531076)
530977 - steel     (C90 - carburetor or injector – replaced by 531146)
531076 - steel     (C90 - carburetor only - replaces 530788)
531146 - steel     (C90 - carburetor or injector – replaces 530977)

In the C90 engines, the original cast iron camshafts were replaced by steel camshafts as follows:

In engines #41602-12-8 and all higher numbers, except #41607-8-8, the #530185 camshaft was replaced by the #530788: and the #530427 camshaft was replaced by the #530977.

Beginning with C90-8F, 8FJ, and 12FJ engine #42205-9-12, and all C90-12F, the cam contour was changed to reduce valve overlap to 24°. The new camshaft number is 531076 for carburetor engines and 531146 for fuel injection engines. (#531146 may also be used in carburetor engines, but #531076 MAY NOT BE USED in fuel injection engines).

IDENTIFICATION OF CAMSHAFTS: Forged steel camshafts are copper plated on the unfinished areas. If the Parko-Lubrite (black) coating covers the area, it may be scraped lightly with a blunt instrument to expose the copper plate. Do not remove the lubrite coating from cam lobes and journals.

 
LIFTER ASSEMBLIES:

A series:

**A21325 (used with A21355 pushrod only).... Includes following:

8     21389 body - hydraulic valve lifter
8     25042 socket - pushrod
8,    21390 unit - valve lifter hydraulic

*A21599 (used with A21509 pushrod only).... Includes following:

8     21608 body- hydraulic valve lifter
8      25042 socket - pushrod
8     531694 unit - valve, lifter hydraulic (replaces 21609)

**Used on A50 engines through #129197
**Used on A65 engines through #404298
**Used on A75 engines through #630398
*Used on A50 engines after #129197
*Used on A65 engines after #404298
*Used on A75 engines after #630398
*Used on all A80 engines

C series:

A21599 (C75, C85, with cast iron camshaft).... Includes following:

8     21608 body - hydraulic valve lifter
8     25042 socket - pushrod
8     531694 unit - valve lifter hydraulic (replaces 21609)

530872 (C90 with steel camshafts #530788 & #530977)... Includes:

8     530873 body - hydraulic valve lifter
8     25042 socket - pushrod
8     531694 unit - valve lifter hydraulic (replaces 21609)

530850 (C90 with steel camshafts #531076 and #531l46 and C145 with #530803 camshaft).. Includes following:

8 or 12     530851 body - hydraulic valve lifter
8 or 12     25042 socket - pushrod
8 or 12 .   533399 unit - valve lifter hydraulic ( 3 to 6 second bleed-down)

A24205 (C125 with #5974 camshaft).... Includes following:

12    24205 body - hydraulic valve lifter
12    25042 socket - pushrod
12    531694 unit - valve lifter hydraulic (replaces 21609)

CAUTION:   Similarity of new and old types of camshafts and valve lifters will require the exercise of caution and care in stocking and installing these parts. It is ESSENTIAL that only steel faced valve lifters be installed in combination with cast iron camshafts, and cast iron faced lifters in combination with forged steel camshafts.

If the large diameter steel lifters #530851) are to be installed in some older crankcases, you may have to burr the case a little so that you will have sufficient clearance for the base of the lifter.  

IDENTIFICATION OF VALVE LIFTERS: Valve lifters may be identified by the thickness of the cam follower "foot" (the disc of the lifter body which makes contact with the cam lobe) at its perimeter. Steel faced followers are all 1/8" thick, while cast iron faced followers are all 11/64" thick. The 3/64" difference is easily noticeable on comparison.


PUSHROD ASSEMBLIES:

A series:

**A21355 (use with A21325 lifter assy. only)

*A2l509 (use with A21599 lifter assy. only)

**Used on A50 engines through #129197

**Used on A65 engines through #404298

**Used on A75 engines through #630398

*Used on A50 engines after #129197

*Used on A65 engines after #404298

*Used on A75 engines after #630398

*Used on all A80 engines

C series:

A21509

Harry

Turning a Box of A65 and A75 Parts into 80 HP

I am about to start covering a scratch built clip wing cub and have been looking for a C-85, 90, or 0-200.  But now I have seen your site and wonder what is possible.  I have a large stash of good yellow tagged A-65 and A-75 parts; cases, tapered cranks, rods, rear cases, cams, etc.  Could you suggest if it is feasible to turn these into about 80 hp. or so?  Experimental, of course.  If it is, how much detailed info can you give me or where can I get it?  I was planning on building up a core engine anyway so if I could do it with some of my stuff that would be great. 

The easiest way to get more horsepower is to turn more rpm.  The A-65 is rated for 2300 rpm redline and the O-200 is rated for a 2750 rpm.  The reciprocating section of the A-65 is nearly identical to the O-200, so why not just turn more rpm?  With the right prop, the engine will develop more thrust simply because the prop is taking more bites of air over a given period of time.  So, if you increase from 2300 to 2750 rpm, the net result is a 19.5% increase in rpm, or rounded to about 20%.  So, by turning more rpm, the engine has 20% more opportunity each minute to turn the prop, and the net result is simply more thrust each over an engine with an equivalent displacement.

However, there are two paths to choosing a prop which will allow the engine to turn a higher rpm- flatter pitch or smaller diameter.  By using a prop with flatter pitch to maintain a particular diameter, the rate of climb performance will increase, but the cruise performance will decrease.  By reducing the diameter, ground roll may increase a bit, but climb and cruise should improve.  Too small of a diameter of a prop can yield diminishing results, especially on a larger airplane like a Cub.

Another path to more power is higher compression ratio.  The A-80 was an attempt to get more horsepower out of the A-65, but the A-80 piston was very heavy.  The net result is that an A-75 piston, combined with higher rpm will likely yield better results than using the A-80 piston.  There are some companies which will build special high compression pistons, but the cost of these pistons is pretty high.  The plain old A-75 piston is a more reliable way to go.

One final method is to install larger bore cylinders.  This is a fairly complicated upgrade, but it will definitely result in more than 80 hp.  Here's a document which describes this change.

Harry

Jetting a Stromberg

Simple - C85 - 0200 cyl, pistons, crank,  rods - Stromberg carb - can't find any info on jetting carb for this conversion.
According to Aircraft Specialties, if the crank is installed per the STC, then no carburetion changes are required.  If your intention is to run the engine as an experimental, and up the rpm from the C-85 level of 2575 to the O-200 level of 2750, then a slight jetting change may be required. 

The Stromberg carb was not approved on the O-200, but was approved on the C-85 and C-90. The parts breakdown for the C-85/C-90 carb list the same part numbers, but the bleed spec for the P16179 main air bleed is -60 for the C-85 and -69 for the C-90. It looks like the bleed air parts are ordered as P16179-60 or P16179-69. Otherwise, the carbs look nearly identical. Here's a parts and maintenance manual which will provide more detailed guidance.

Harry

Erratic Tach

My Fly Baby has a C-85-12E and an AC Tach (that's what it says on the dial at least).  Tach dial rotation is clockwise, the tach drive on the back comes off pointing down and to the left (e.g., not straight out the back of the tach).

Runup and takeoff were normal, and the tach worked properly through most of the flight.  I came back home to do some T&Gs.  On a downwind for one of them, I noticed the tach needle was bouncing all around.  It did it the rest of the flight.  I did a runup after the full-stop, and it definitely never stabilized though the engine was running smooth.

So...either the tach, tach drive, or tach cable.  Is there any good way to tell?

Two other items of interest.  There's been a drip of oil coming from where the tach cable connects to the engine case.  My A&P even suggested it could be the source of my leak, though I've never seen THAT much oil associated with it.

Second...well, it was raining.  The tach squirreliness didn't begin until I'd been flying in the rain a couple of minutes.

It could be something simple, like the tach cable nut has backed off at either the tach or engine side.  The center cable of the tach is round, but squared and tapered at the ends to fit into the female ends of the tach and tach drive.  Sometimes the cable retaining nut backs off and the drive cable can slip out of the female drive and the tach kind of jumps as the cable periodically catches a position where it will drive the tach, and drops to zero when it is out of position.  This would be my first guess.

The tach center drive cable may also be dry, in which case it twists, and then untwists due to the drag between the center drive and the outer casing.

The center drive cable may have broken, and is driving against the broken point.  Unlikely, as once the cable breaks, it tends to go straight to zero.

On the engine side, the tach cable is driven by a forked shaft in the end of the oil pump gear.  The fork can break, but it is rare.  But, an oil leak in this area may be a sign that there is a problem.  If one of the forked tangs breaks, then it will likely wobble in the seal in the engine tach housing, resulting in an oil leak.

Finally, the tach could have just gone bad.

Ok, so on to the troubleshooting-

The easiest part to check is the connections of the tach cable to the engine and tach.  Basically, just a couple of thumb-turn nuts which attaches the cable.  Check to see if they are seated, and run the engine to see if the problem repeats.

If the problem repeats, then on to checking the center drive cable.  It is easiest to just pull the tach out of the panel (you will probably bench check it, anyway).  On the engine side, disconnect the cable from the engine drive.  When the cable is screwed off of the engine drive, the forked tangs from the oil pump gear will be exposed.  Just wiggle the tangs with your fingers to see if they are loose.  If there is a problem, it will not be subtle- one of the tangs will easily fall out.  To further expose the tangs, the tach housing can be removed.  If you have an oil leak, you will need to pull this housing, anyway.  There is a small oil seal in the housing which can be replaced.

Ok, if the forked tangs appear to be intact, then check the cable for continuity.  A helper will be needed for this step.  First step is to push the inner drive cable back and forth, and to pull equally at each end to confirm continuity.  Sometimes the inner drive cable can be pulled through the outer sleeve (sometimes not, as it may have a lock to prevent the cable from walking in and out of the housing).  If the inner drive can be easily pulled out of the sleeve, then pull it out and lube it with motor oil.

Now, if the tach drive is good, and the cable is good, it could be the tach.  However, lubing he cable may have solved any twisting of the inner drive cable, too.  So, rig up a drill to turn the tach.  I'll leave the details of driving the tach for you to figure out, but this should be easy.

Finally, swap the tach head with another unit and see what happens.  This can actually be done a earlier on in the troubleshooting process.  If you need a test tach, I've got one I could loan you.  The old AC tachs are pretty reliable and I have rarely seen a failure, and if they do fail, they usually just read off, not erratic.  They can be rebuilt, though.

Harry

Running Rich on Just One Side

My C150 G is the reason for asking for help. The engine is running super rich on the L/H bank and just nice on the R/H bank. I have blanked off the primer system to rule it out, the compressions are all 78/80, the ignition timing is spot on (28 Deg), the engine uses 1/2 quart in 25 hours running and there are no obvious induction leaks. The Carb has a "V" stamped on the data plate which I assume indicates a 1 piece venturi. Can you think of anything I have missed ?. Looking forward to your help here

Since the O-200 is carbureted, and all of the induction tubes are linked to a central flow divider, commonly called the intake spider, a problem with the carburetor would cause trouble with all of the cylinders.  The fuel/air charge is going to be balanced to either too rich for all cylinders, too lean for all cylinders or somewhere in the middle.  The primer attaches to the intake spider, and a leaky primer usually affects the engine at low rpm, resulting in an rough idle.  So, reasonably speaking the intake and carb are not likely to be the problem.
So, the issue has to be with either airflow to the cylinders or the cylinder itself.  If there was an intake leak, then that leak would cause a lean running issue.  In this case, the plugs would be too clean with almost no combustion deposits as the cylinder fuel/air charge would have more air than fuel.  This kind of problem is very noticeable and is usually accompanied by backfiring sounds in the exhaust.

A very likely problem is that the intake valves are leaking on the sooty cylinders.  When the intake valve develops a leak in the valve to seat seal, that cylinder will be drawing a fuel/air charge over too long of a time span in the combustion cycle.  An intake valve leak is different in nature to a straight intake leak.  As stated, an intake leak draws too much air, leaning the mixture.  If the intake system is closed and not leaking, fuel and air are always present.  If the intake valve does not seat, then fuel/air is pulled into the cylinder any time the piston is pulling suction.  The net result is that there is a cumulative excessive intake of fuel and the plugs foul.

An intake leak can be determined by conducting a differential compression test.  When air is applied to the cylinder it may hold compression and make the basic go/no go numbers, but leakage through the intake and exhaust valves cannot be permitted, despite the apparent "good" compression.  An intake leak will be detected by listening for air hissing through the intake where the air filter attaches.  I'm sure that if you check the engine, the cylinders with clean plugs will not leak air, and the cylinders with sooty plugs will probably hiss air into the intake. 

Continental Service Bulletin SB03-03 details how to properly inspect cylinders.  The gist of the this SB is that the seals of the valves need to be perfect.  Here is a link to the SB: http://www.tcmlink.com/pdf2/SB03-3.pdf.

Don't read too much into why the LH bank is showing the problem.  I just finished repairing two engines with this condition.  One was an A-65 in a Mooney Mite and the front two cylinders were the problem.  The other was an O-200 in a Cessna 150 and the RH pair of cylinders showed this problem.  All of the affected cylinders had intake leaks, most likely due to overly aggressive leaning.  In both cases the owners mentioned that they were leaning aggressively to clean the sooty plugs.  What happened was that the aggressive leaning overheated the valves and made the rich burning problem worse as the high temps caused the burned seat at the intake valve to erode faster.

You do mention the one piece venturi.  It is a common problem for the one piece to run very rich, unless the "pepperbox" nozzle is installed.  The pepperbox nozzle has a series of holes at the end of the discharge tube to atomize the fuel spray and the standard nozzle has just an open tube.  The thinking was that the two piece venturi had enough sharp engines to atomize the fuel flow, whereas the one piece was too smooth and the mixture did not atomize properly.  Actually, the problem was so bad, that Precision and the FAA allowed the use of the two piece venturi (albeit with frequent inspection) to cure the rich running problem.  So, if you have a one piece venturi, and no pepperbox nozzle, it is possible that this engine has been leaned too aggressively to "fix" the rich running of the one piece venturi. Unfortunately, this "fix" may have caused other problems.

Harry

Worn Oil Filler Neck

I have a 1940 Piper J4 Cub, restored with a C85-12 Continental engine overhauled and installed during restoration.  We have a problem with the oil filler cap (w.dipstick) not fitting as tight as it should.  We thought it was the tabs on the cap but after further examination, it appears to be that the inside of the filler neck where these tabs fit is simply worn down.
 
I swear that I saw an ad where you could purchase just the top portion of the filler neck, cut the old off and weld on the new.
 
Any ideas on how we can fix this problem??
 
Wear at the tabs at the top of the oil sump filler neck is a common problem.  The top of the neck tends to rust due to water vapor boiling out of the oil and simply due to friction wear between the cap and neck over, say, 60 years.
 
I have not seen an ad for a new neck or top.  If such a product exists I’d like to buy about ½ dozen right now to fix various tanks.  I wonder if this is something sold by Univair?  This company still makes complete new sump tanks (although at a price!)  I’ll do some looking around.
 
Otherwise, I don’t have a really good solution as I have a couple of sumps in exactly the same condition.  I have seen a sump neck modified with a couple of screws which serve as an anchor for a hoop of wire which snaps over the top of the oil filler cap.  Kind of the same principle as the wire which holds most sump bowls on.
 
Let me know if you find a source for a replacement oil sump!
 
Harry
 

C85 Stumbling

Good afternoon, Harry! I am having a problem with a C85-12F engine. I  got this aircraft into my shop and when it came in the problem was that it would die on acceleration and then would have to be primed to restart. It has a Stromberg NA-S3A1 carb on it. I checked the intake and no intake leaks, so, I rebuilt the carb and it did the same thing, died every time I would advance the throttle. So, I figured the carb was defective and found another NA-S3A1 carb. Overhauled this one and put it on the engine. Ran up the engine and it no longer dies on acceleration and I do not have to prime it every time it shuts down. The problem that I am having now is that the engine stumbles on acceleration from idle. If I am at 900 or 1000 rpm’s it advances just fine although there is a bit a roughness when I just start to move the throttle. What do you think the problem could be?
 
It is most likely that the idle mixture is too lean, and the engine simply starves for fuel transitioning from through the “off idle” transition point.  Another clue if the idle mixture is too lean is if the engine backfires slightly when the throttle is cut back to idle.
 
There is a thumbscrew on the flange of the carburetor which is screwed in to adjust the idle mixture (not the idle speed).  Enrichen the mixture and advance the throttle to see if the stumble diminishes.  Most of the time, the condition you describe is caused by a too lean idle mixture.  After you adjust the idle mixture you will probably need to re-set the idle speed by adjusting the idle speed set screw.
 
If this doesn’t do the trick, then it could be that the air bleed circuit which transitions from idle to full throttle has a bit of fuzz in it.  It does not take much to block the airway and cause a problem.  DO NOT use compressed air to blow out the passage as this can create a negative pressure in the float bowl and collapse the float.  The most correct way to fix this problem is to disassemble the carb blow out the air passages.  Even better, soak the carb half in an ultrasonic cleaner to break any obstructions loose and then clear the passages with air.
 
Page 87 of the Bendix-Stromberg Carburetor Manual is a Service Bulletin which describes problems with off idle engine stumble, primarily in cold weather and idle during glide.  The summary of this document is that the idle mixture may need to be adjusted for certain weather conditions.  It is not unusual to enrichen the carb a bit during cold weather and lean during warm weather.  See Continental Service Bulletin M64-6 which also discusses cold weather operating problems.
 
Try enriching the idle mixture and let me know if that works.
 
Harry

Follow-Up

Well, I adjusted the idle mixture and it seems to be working. Very small stumble, but not really a stumble, kind of a small shake as it starts to accelerate. There is one problem that the customer called and told me today after he got home and that is that he is not developing full rpm on his takeoff roll. He said that he was getting 2500 rpm but it seemed to only get to 2300 today on takeoff. Is there something else going on? Also, I noticed a lot of black sooty smoke coming from the exhaust. Is this because it is suck a rich mixture? He is also using auto fuel.

Well, it sounds like there is a problem which is more than just the idle mixture.  If the engine is not turning up rpm and the exhaust is sooty, then there is a problem and the plane should be grounded until this is sorted out.  This is clearly not normal operation.  The customer complaint about engine operation coincides with the carb work, and auto fuel would not suddenly result in this kind of problem.
 
You mentioned that you found a replacement carburetor.  Was the venturi and jetting correct for this engine?  The Stromberg carb has a generic look, but the venturi size and jetting vary from carbs fitted to specific engine models and sometimes the airframes. Don’t trust the part number stamped on the carb flange!  Parts can easily migrate from carb to carb, regardless of the part number stamped on the carb.   Do some homework using the carb manual I sent to you plus the airframe parts manual to make sure that the carb is set up with the right parts.
 
Assuming that the carb parts are correct, then there could still be a problem with obstructed airflow in the bleed air circuit, incorrect float setting, or there is a problem with the mixture plates in the mixture circuit.  Even though the mixture circuit is usually wired closed, the mixture mechanism must be in place, and function, for the carb to work properly.
 
I have attached three articles from the Cessna 120/140 website which really provide a detailed description, complete with diagrams, on how the fuel flow circuit works and the overall theory of operation of the Stromberg carb.  Start with the article on “Stromberg Mixture Secrets” and this will give you some excellent details on the theory of fuel flow through the Stromberg carb.

Stromberg Mixture Secrets
Stromberg Fuel Level and Tools
Stromberg Carbs: Needles Leaking, Safe, Or Take A Chance?

Unfortunately, you are in that loop of getting sucked into a seemingly simple job which becomes increasingly complex.  One of the benefits of using an accessory shop is that they are experts and have all of the tools for this type of work.  A shop mechanic may look into a carb once a year, whereas an accessory shop looks at five or more each day, every day.
 
One final thought- are you sure that this engine does not have a leaking intake valve, or valves? A leaking intake valve can cause the engine to run rich.  I find this problem many times on four cylinder Continentals.  The engine will pass the compression test, but the air leaking through the intake valve is missed.  When air is applied during the compression test, air should not be heard hissing in the intake or the exhaust.  See the Continental Service Bulletin.
 
Harry
 

McDowell Safety Starter

I just saw the post about the McDowell safety starter, that is pretty cool. Does it seem to work well?
Are they available?

I did some searching over lunch, here is what I cam up with...

http://www.aeronca.com/manuals/airplane_starter_patent_2266098.pdf
http://www.joea.com/mcdowell_safety_starter_information.htm
http://www.vintageaircraft.org/featured/2003%20-%20Vol.%2031,%20No.%2010%20-%20Aeronca%20the%20Hard%20Way.pdf   ( pic of handle in body of article.)

Anyway this is good news, now if this thing isn't unobtainable I'll be set!

Once again, a tantalizing solution which is practically unavailable!

Give or take some adjustment, the McDowell starter actually works quite well, especially with impulse coupled Slick magnetos.  It is the same concept as a lawnmower pull rope starter- a pull via a lever pushes a sprag into a tooth on a ring gear.  When the lever is released, a spring pulls the sprag assembly backwards to position it to catch another tooth for another pull.  A lever in the cockpit was pulled, and the engine would snap through one blade for every pull.

The problem is that the starter is very rare, and also highly sought after, which has pushed prices very high.  They do come up for sale from time to time, but sell for $1000 to $2000!  The starter was kind of a pricey option in the 40’s, so not many were sold.  Of the ones that were sold, these devices quickly became a maintenance headache and were stripped off and thrown away.  So, the supply of these starters is really limited.

There has been talk of re-producing the McDowell starter, but I don’t think that this has come to pass.  It is a bit complicated to retrofit because the mechanism has to have bracketry in the airframe and modifications made to a standard cowl.

Overall, though, this is one of the better solutions, though.

Harry

Exhaust Stud Removal

I have an A-65, about 270 SMOH, 1500 TT, on a Wolf Boredom Fighter. I removed the left exhaust stack to repair a crack and found the stack flange was slightly  vibrating on the flange mounting stud. That and a little blow-by have started to cause some erosion of the stud, so I’d like to replace it now, rather than later. What’s the best way to remove one of these studs from the cyl. head?

The proper tool is something called, of all things, a stud removal tool.  This tool is an internally threaded device which looks like a socket.  When turned, it grabs the OD of the stud- kind of like an “inny” EZ-out.  KD tools makes this tool or do a Google search for stud removal tool.  The tool will be sized to the OD of the stud to be removed.  Sears or most auto parts stores sells these tools.

The poor man’s way to do this is to thread two nuts with a lockwasher between the two nuts.  Tighten the nuts together, and then turn the topmost nut against the bottom nut.  If the stud is not anchored too tight, then it will turn out.

BUT- be careful.  Sometimes these studs become very tightly anchored in the cylinder and it is very easy to break the stud off in the head.  This becomes a big problem as it is fairly difficult to drill out the broken stud.  In fact, it is a near certainty that the cylinder will have to be pulled to put it into a fixture to drill out the broken stud and get the new threads square.

So, carefully heat the cylinder head to expand the aluminum away from the steel stud.  Gentle heat from a heat gun or a propane torch should be good.  Obviously, the aluminum can only take so much heat.

When you install a new stud, be aware that new studs come in standard and oversize thread sizes, and the oversize studs have a number of oversize fits.  I would recommend having a standard and the first oversize stud on hand.  Install the one that seems to fit the tightest.  Don’t use Loctite  as this will really make the stud tough to remove at a later date.  A mechanical fit is the best as the grip can be release with a bit of heat, whereas the Loctite tends to remain fixed regardless of heat.

Harry

Oily Plug

Here's a problem from the UK. I can't find anyone here with the answer.

Last year we fitted Millenium cylinders to our 0-200 installed on a Rollason Condor. We checked the compression and got about 75 in each cylinder.  Fairly soon after this we started to get a mag drop (right OFF) on first start of the day after a long time standing. This usually clears after running at 1700 rpm with a lean mixture. Once cleared there is no sign of a mag drop for the rest of the day which might include 2 - 3 hours flight time with probably 3 - 4 starts.

The oil consumption has been about half a pint per 20 hours. Some of this is leaking, probably from the No 4 push rod tube.

The first time we removed the plugs, and several times since, the No 4 lower was very oily.   More recently it has become more difficult to clear the mag drop, taking about 30 seconds leaned at 2000 rpm. Once we couldn't clear it at all and had to change the plug.

Last plug change we had no oil on the plug but, using a borescope, thought we could see a small pool of oil on the cylinder. There was no apparent damage visible.

It has been suggested that this could be due to a misaligned oil scraper ring. Can you suggest any other possible source of liquid oil entering the cylinder when it is cold?

Thanks for your help,

Sitting here  at my computer, half a world away, I can only make a guess.   I don’t think that it is a problem with ring gaps aligning.   However, I would guess that the oil control ring may be broken.  I see this problem a lot, and I keep spare oil control rings on hand because I sometimes will break one while installing a cylinder.  The problem is that the oil control ring is at the bottom of the piston and it is awkward to slip the cylinder over the ring because the rod wants to walk on the crank while the cylinder is being slid on.  When the rod shifts, the ring can pop out of the clamp, catch on the bottom lip of the cylinder and then break.  When installing the cylinder, position the crank with the rod at the outermost length of its throw.  This will provide the maximum clearance during assembly, and your helper can hold the rod while the cylinder is being pushed over the piston.   Once the piston is in the cylinder, turn the crank to pull the piston/cylinder assembly closer to the engine crankcase as opposed to fighting pushing the piston further into the cylinder.

If the ring is not broken, it is possible that the oil scraper ring was installed upside down.  There is a bit of a bevel to the ring, and the bevel should scrape oil out of the cylinder, if properly installed.  If it is upside down, then the oil will be pulled into the cylinder.

Another possibility is that the cylinder has not broken in properly.  If this happens, the cylinder wall will glaze and actually have a mirror-like polish.  The surface needs to be slightly honed to retain oil at the surface.  If the surface is too polished, then the oil drains off of the cylinder wall and puddles at the low point in the cylinder.

A final, but probably remote possibility is that a valve guide is leaking.  If the guide leaks, then oil is pulled into the combustion chamber when the valve is open on the intake stroke.  A telltale sign of this problem is a pattern of yellowish deposits on the combustion head beneath the offending valve seat.

My bet however, is a broken oil control ring.  The fix, of course, will require pulling the cylinder to inspect.

Harry

First Start After Long Period in Storage/Rusty Sump

The A-75 engine I bought was overhauled in 1977, topped in 1981 and the last flight was in 1985 with 227 hours SMOH. It sat for 14 years & in 1999 it had a "condition" inspection, torn down, inspected & anything needed replacing was done. It was declared airworthy but still sat idle. In 2004, the mags were overhauled. All of this was done in Arizona or somewhere out west. In Sept. of 08 it came to me in Ohio & since then has had desicant in all the openings and dehydrator plugs installed. My plan is to scope the inside for signs of rust, if it looks good I'll put the oil & fuel to it, taxi it extensively, check for leaks & compression before flying it. Does this sound like a reasonable plan to you?
 
The inside of the oil tank does have rust, can this be removed?
 
When it comes time to run the engine, there is not much to do other than to run the engine.  It makes sense to borescope or at least look at the cylinder walls through the spark plug hole just to catch any obvious rust.  Frequently,  the cylinder rusts near the top, which is difficult to see through the spark plug hole.  I would probably do the first run on non-detergent break-in oil and run the engine on the ground a minimal amount.  Too much ground run time, like more than 30-45 minutes total time, will glaze the cylinder walls due to uneven cooling.  Run the engine to get it warm, shut down and do a compression check to make sure that the rings and valves are sealing with no major problems.  After that, just fly.  The first oil change or two may yield a streaky, caramel colored oil.  This is not unusual as the remnants of the assembly and storage liquids will be in the residue.  The second or third oil change should look like normal, dirty oil, if that makes any sense.

Regarding the sump, you can remove the sump, polish it with Scotchbrite, but this is a tough job depending upon the size of your hands.  Big hands have a tough time getting into the small hole.  It is not unusual to see some light surface rust, but you shouldn’t see crusty or scaly rust.  This material can be abrasive and cause wear.  It is not unusual, though, to see rust in the sump neck as this tends to be a “chimney” of sorts for condensation to boil upwards out of the oil.  If you remove the sump, new gaskets are easily found via Aircraft Spruce or Fresno Airparts.

Harry

Baffling Under the Cylinders

Concerning the baffle tins that go under an A65's cylinders: One mechanic tells me that each cylinder has two; another mechanic tells me that each cylinder has only one such baffle.

So which is it????  Thanks a lot.

Baffling is usually determined by the airframe manufacturer.  Continental supplied engines, but no baffling, although they provided the airframe manufacturer with guidance on cooling.  Baffling is different from airplane to airplane.

Usually there is an intercylinder baffle in between the bottom of the cylinders , and a flat piece which fits in the cylinder fins with a wire between the bottom baffle piece to hold everything in place.

I have attached an article on intercylinder baffles which will probably answer your questions in detail.  Also, here is a link on engine cooling.

http://www.littleflyers.com/engcool.htm

Harry

O-200 Mag Timing

I have a 1969 Cessna 150J. It has the Continental 0200a engine. All the cylinders are 73 to 75 over 80. We are using 100LL fuel & UREM40E spark plugs

The timing was at 34 degrees and on mag check we got a 100 rpm drop. The engine plate says to use a 24 degrees . We reset it to 24 degrees and the mag check showed a 200 rpm drop on the mag check and a bit rough sounding with both mags operating. We reset the timing to 30 degrees and got a 150 rpm drop and smoother running engine, good idle and good lean. What are your suggestions on the timing.?

Since you are operating an FAA certified aircraft, there are no options on timing other than to follow the engine manufacturer’s specifications.  Here is a link to the Continental Service Bulletin which provides the details on magneto to engine timing:  http://www.tcmlink.com/pdf2/MSB94-8C.pdf

The O-200 has very specific timing requirements under FAA AD 96-12-06.  This AD requires setting the magneto timing of both magnetos on O-200 engines with one or more cylinders having part numbers lower than 641917 to 24° BTC.   But, for engines with all four cylinder having part number 641917 or higher, or Superior or ECI cylinders, it is authorized to reset the magneto timing of both magnetos to 28° BTC. The change to 24° BTC had been made to prevent cylinder cracking.

When the TCDS was originally changed to show 24° BTC on both mags, it resulted in a loss of power. The authorization IAW AD 96-12-06 to change the timing to 28° BTC if all cylinders are p/n 641917 or later restores that lost power.  However, the power which is lost is barely noticeable under routine operations.

The typical maximum magneto drop is a max of 150 rpm for an individual magneto, with no more than a 75 rpm difference between the two magnetos.  Both magnetos may not provide exactly the same magneto drop, 75 left-125 right, for example.  The split should not be more than 75 rpm between the two magnetos, though.  If you reset the magneto timing to the correct value and the engine runs too rough or the magneto drop is out of spec, then there is a problem which is being masked by the advanced timing.  The real problem is not that the engine runs better at an advanced timing, but that it does not run well at the correct timing.  Tens of thousands of O-200 engines run perfectly fine at 24 degrees of timing, so the FAA approved timing setting will not cause problems.

Harry

Getting Plungers Out of Tappet Bodies

Corrosion has found its way into my C90 so I have to take it apart for replacement of parts.  How can I get the plungers out of the tappet bodies? I have tried with a piece of wire but it doesn't help.

Is there a snap ring in the top of the tappet body which holds the pushrod cup in place?  The snap ring is a very small wire and might be hard to see.  The pushrod cup should fall out very easily, so if it doesn’t, then the snap ring is still in place.

If the snap ring is out, then try soaking the tappet body assemblies in solvent or a chemical like MEK to loosen any oil which may be keeping the parts from separating.   If this doesn’t work, a heat gun can be used to heat the outer diameter of the tappet body.  Heat the tappet body and use a magnet tool to pull the hydraulic unit out.  If the heat gun does not work, then a gas torch at a very low setting could be used to heat the tappet body, but be very careful as too much heat may damage the tappet.

Harry

Continental Cylinder Break-In Problems

Harry- I have a 1940 J4-A with an upsized C-85 (O-200 crank, cylinders, and pistons).  The prop is a 74 X 42 McCauley (I think).  The engine has less than 200 hours on it and I have replaced 3 pistons in the rear.  Number 1 has been replaced twice.

My A&P thinks the problem is baffling (no pun intended).  (Only once have I seen oil temp climb above 160 degrees).

My A&P had replaced both pistons and rings. The compression was 17/80 and 21/80.  The rings were frozen into the pistons and the sides of the pistons were severely scuffed.  You could still clearly see the hone marks on the cylinder walls.  The cylinders were purchased new from Millenium in Jan. '06 (steel). (This was part of a complete engine rebuild) Last year, no compression in No. 1 (0/80) and the mechanic (a different guy than this year) replaced the rings and piston, also.  Also rings frozen into the piston.

Perhaps a little info on how the plane is flown.  I'm probably the biggest 'Momma's Boy Pilot' you ever saw.  I don't climb out hard, I don't continually run up against the firewall, I don't overspeed the engine in a dive.  When I had the engine rebuilt, I installed an oil filter (remembered to cut the Cat Catcher screen out) and still change oil every 25 hours. (although I have my wife convinced that an airplane is about as inexpensive to operate as a motorcycle, I know this thing is expensive and I want to minimize that as much as possible)


This is not the first time I have heard of this problem, but not just limited to Superior cylinders.  Over the past few months I have heard problems with Superior, new Continental and overhauled Continental cylinders.  No clear common denominator except that there was some similarities in how the engines were run after cylinder installation. Primarily, the engines were not run hard enough or too infrequently during break-in.  Another common thread was that every single engine was repaired and run-in during colder temperatures of late Fall-early Winter.

The Continental requirements for cylinder break-in can be found at this link:  http://www.tcmlink.com/pdf2/M89-7R1.pdf

In summary, Continental recommends a minimum of ground run operation, just enough to get the idle and mixture set up.  Then, break in the engine by maintaining 75% minimum power for the first hour and then alternate between 65% and 75% for the next two hours of flight time.  The flight time should be continuous and avoid touch and go operations until the engine is broken in.  Many engine overhaulers recommend near full throttle operation for the first couple of hours.  In short, don't baby the engine too much- run it a bit hard in the first few hours to get the rings to seat.

Another factor is overall temperature of the engine and especially the engine oil.  If the cylinder operates too hot, then the ring can lose its "temper" or spring-like tension qualities and become unable to hold surface tension against the cylinder wall.  When this occurs, oil is pulled into the combustion chamber and burned or heated to the point where the residue becomes sludge and binds up the rings.  At the opposite end of the spectrum, if the engine operates at too cold of a temperature, then the oil may not lubricate properly, resulting in excessive friction and rapid wear.  Once again, if the oil is pulled into the combustion chamber it can result in sludged up rings.

If the cylinder bore is worn or flawed, then the problem will likely repeat as it would make sense that new pistons and rings would change the parameters for sealing the cylinder bore.  If the cylinder is out of spec, then the problem would be likely to repeat with repeated installations of pistons and rings.

Here is a link to some information on this topic: http://www.tpub.com/content/engine/14075/css/14075_105.htm and http://www.sacskyranch.com/eng22.htm

Given that you have reported that your engine runs very cool, this could be the root cause of the problem.  The oils may not be getting warm enough to lubricate properly or boil out suspended contaminants.  If your engine is running as cool as you think, then you may actually need to restrict the outflow of air at the bottom of the cowling to pull the engine temperatures up so the oil is operating at about 180F.  I have attached an article which describes how the outflow of air affects engine temperatures.  Although primarily for winter operations, this will give you some ideas on the effect of engine outflow cooling.

By the way, all of the above discussion regarding temperature assumes that your gauge is reading correctly.  Dip the oil temperature sending bulb in boiling water.  Water boils at 212F, so the temperature gauge should read that number when the sender is immersed in boiling water.  Food for thought, it may be worthwhile to buy a cheap multi cylinder CHT gauge to get a feel for the engine temps.  EGT's are not as damaging as CHT's with your particular problem.

Contact the Cub Club group as I am sure that someone will have experience  with the J-4.

Harry
 

Stuck Piston Rings

I have an A65 Continental on a Pietenpol Air Camper. The engine was rebuilt in 2004 with new Millenium cylinders and pistons, and now has 138 hours on it.  Lately I had noticed one cylinder being very weak when hand proppong, although the engine started and ran normally and gave normal static and flight RPMs.  At its annual condition inspection last week, I found that the cylinders had the following compressions:  #1 – 74/80, #2 – 58/80, #3, - 76/80, #4 – 38/80.  At last year’s inspection all cylinders were in the mid 70’s.  Note that the engine was warm when compression was checked.  Both low cylinders produced hissing at the breather tube, and during the ground warm-up I could see mist blowing out the breather tube.

I pulled cylinders #2 and #4 and inspected them.  Both cylinders appeared to be fine with no obvious burning or any other problems on the valves.  It appeared the cylinder walls were glazed and the top compression ring on each piston was stuck tight with the gap compressed almost closed.  On #4 the lower compression ring was sticky and would not easily move, and the gap was in line with the oil ring gap.

What causes piston rings to stick like this?  I first noticed the weak cylinder after flying almost 14 hours in one day on the way to Brodhead.  I took the cylinders to the local mechanic to have them honed and new piston rings installed.  Tell me what I need to do to prevent something like this happening again.  Someone mentioned that I should be running Marvel Mystery Oil in it.  I have run a steady diet of Aeroshell AD Oil W 100 since it was broken in (broke it in on straight mineral oil).

Cylinder glazing is usually heat or cooling related.  I see glazing frequently on engines which have been run on the ground during an extended break-in process.  Never run the engine on the ground for extended periods.  Run the engine long enough to get the carb set up and check for leaks.  Break the engine in while flying to get adequate cooling over the cylinders.

 Ok, looking at your description, it is interesting to note that the cylinders on the left side are the only two with the problem.  I wonder if P-factor and the swirl of the cooling flow of the prop has any effect on the differential in cooling?  Otherwise, it could just be coincidence.  The pictures of your Piet show a fairly conventional engine installation.  The eyebrows look to be a bit taller than the J-3 type, but I’m not sure if this would cause a problem.

 Do you have inter-cylinder baffles?  These are bits of curved baffling which go in-between the cylinders to guide air around the bottom of the cylinders.  I’ve attached an article which describes the purpose and placement of the baffles.  If these pieces are missing, then this surely could be the source of your cooling issues.

 The rings are probably stuck in the ring groove of the piston due to sludge build up from the oil.  If the cylinder walls became polished, then oil probably accumulated in the combustion chamber.  I usually see this type of problem when used pistons are worn beyond limits and new rings are installed.  The rings kind of walk in the ring land and the sealing edge of the ring that contacts the cylinder wall wears rapidly.  I think that the Superior cylinders come with new pistons, so this probably wasn’t the problem.

 Finally, it could be that you got a bad set of rings.  I saw this exact same problem with a Cessna 140 and a Luscombe with Continental engines fitted with Superior cylinders at my airport.  We wresteled around with the problem and finally fitted TCM factory rings and solved the compression and oil burning problems.  I could never really prove that the rings were bad manufacture, but the problem went away when the Superior rings were changed to TCM rings.

Regarding break-in, don’t baby the engine.  The engine needs to be run at no less than 75% power or more for the first continuosu hour, and between 65% and 75% for the next four hours.  Flying engine in the pattern and doing touch and goes will not result in a good break-in.  Fuel up and plan to run it hard for the first five hours to ensure that the rings seat in properly.  Here is a link to TCM’s bulletin on engine break-in:  http://www.tcmlink.com/pdf2/M89-7R1.pdf.  Mineral oil is the standard for the first few hours, and then run standard detergent aircraft oil from the next oil change on.  The A-65 requires 25 hour oil changes if there is no filter installed.

One more thought- what do you see for oil temps?  Open cowling engines tend to run TOO cool, and high oil temps of 140-160F are not uncommon.  The subtle problem is that the engine may not get warm enough, although I would have to do some research to see how this would affect cylinder glazing.  It could be that the oil does not get viscous enough, which would reduce the lubrication properties and maybe result in glazing.

Finally, Marvel Mystery Oil is aptly named.  I can say will all confidence that there is no consensus as to whether MMO works or does not work.  From my view at the top of the mountain, my observation is that there is no scientific proof that MMO helps any engine condition.  On the other hand, there does not seem to be any significant evidence that MMO cause harm to engines.  So, my simple answer is, it probably can’t hurt your engine to use it, but don’t expect miracles.

Harry

Follow-Up

Thanks, Harry.  A little more information for you:

I do not have inter-cylinder baffles.  I didn’t think they were necessary with the open cowling and Cub – type eyebrows (my old J-3 Cub didn’t have them either).  Based on your information, I think I will add them.

On the trip to Brodhead this year (13 hour trip from North Carolina) at about the halfway point the bracket securing the eyebrow to the # 4 cylinder rocker-box broke, allowing the eyebrow to splay out and almost certainly disrupting the airflow around the back of that cylinder and decreasing the cooling air to # 2.  I safety-wired the bracket back together at the next fuel stop.  That repair lasted nearly 15 minutes.  When I got to Brodhead, I drilled out the rivet holes in the cracked bracket and replaced the rivet with an AN3 bolt and nut. A that time I first noticed the loss in compression on one cylinder so my guess is that I glazed the cylinder on the way to Brodhead.  Attached photo (Brodhead2008 123) shows the bolted repair as I was hopping rides at Brodhead.

The bolted repair lasted until I was only about an hour from home on the return trip and then it broke again, along with the bracket attaching to the # 2 cylinder rockerbox.  I took the attached photo at this time.

Once home I made steel brackets to attach the cooling shroud to the rocker boxes.

Obviously I should have repaired the cooling shroud much more thoroughly when it first broke.  I have seen a Rose parakeet with no cooling shrouds at all and assumed that if it could fly without cooling shrouds my damaged shroud would not be much of a problem.

Thanks for your help.  I think inter-cylinder baffles make more sense than Marvel Mystery Oil.  Do you remember what timeframe you had bad rings from Superior?  I bought those cylinders in about 2002.

Interesting that the problem was on the side where the baffling broke loose.  While there is no real science to connect your problem to this event the coincidence is noteworthy.

I know the Parrakeet which you are talking about.  I actually looked at it from the opposite direction and figured that sooner or later this operator would experience problems.  My approach may be simplistic, but I work from the weight of numbers.  The Cub shrouding system and inter-cylinder baffles has been proven to work well, so why fight the system?  In many ways the motor makers of the 1940’s were much more in tune with their product than the companies of today.  If the old timers had a baffle in place, then there must have been a good reason.
 
The ring problem I experienced was the Fall of 2001, but the rings had been installed during Spring of 2000.  Keep in mind that I have no idea when these rings were manufactured or how long they were on the shelf.  So,  I don’t have a lot of proof that there was actually anything wrong with the rings except that there were a couple of instances which occurred at about the same time.  There were probably another six or eight airplanes in my area using the same rings which never had a problem.   At the time I discussed the problem with Superior and was told that they never experienced any problems with their rings, and the end user probably broke the cylinder in poorly.  How do you prove right or wrong in this case?  You can’t, so you fix the problem and move on.  Incidentally, after replacing the rings and honing the cylinder neither of these planes have had a problem over several years and a few hundred hours of operation.

Anyway, build some baffling parts and see if this won’t change the parameters of your problem to result in better success.

Harry


Mixing Mags

Hi Harry, Thanks for your column it has been most helpful....But here's  a question .. My 0-200 has over 3000 hours on it. 1000 odd since last  time overhaul.( I have the full history)  The Bendix mags are the same  ones and have run 500 hours since being checked. I have aquired a new Slick mag quite cheaply. Can I mix one Bendix and one Slick while I look  for another new Slick? If I time them the same I can't see any  problems.BUT I would like to get your opinion. I could ask locally , but  everyone has an axe to grind!

The FAA Type Certificate Data Sheets specifically require two like magnetos, i.e., two Bendix or two Slick magnetos of matching model numbers.  Here is a link to the FAA TCDS.  Check out the last item on page 1.

I am not sure how amateur built aircraft are handled in Australia in the respect to conforming to approved data.  I'm sure that CASA has adopted much the same TCDS wording as the FAA, so the statement regarding two like magnetos will be in their system, as well.

However, from the operational standpoint, all approvals aside, mechanically, the Slick and Bendix mags are identical in the respect that both mags provide a lagged 25 degree starting spark, and will deliver the running spark at the same advance timing setting.  The only difference is that each magneto is physically different (yet operates identically).  So, there is no physical limitation to using a mix of two different magnetos, so long as the basic lag angle and timing is the same.  A consideration, though, is that the fit of the ignition harness to the magneto is different, so different ignition harnesses will need to be used.

I reckon that it will boil down to whether or not the engineer in charge will accept two different magnetos, regardless of the fact that both mags operate identically.  Ultimately, the engineer is going to have to sign his name to the airworthiness, so he is the one who has to be comfortable with that decision.

Harry

Backfiring 0-300

I have a cont. 0-300 in a 1957 Cessna 172 recently I started using auto gas, the mixture in my tanks right now is half avgas half car gas. It seems now that whenever I reduce the throttle to land the engine starts to backfire.  I have always leaned the engine aggresivly using avgas,should I change my leaning habits using mogas and could this backfire problem be a result of this.

Your problem may not be exactly fuel related.  I get lots of complaints about auto fuel with symptoms which are nearly impossible to diagnose as being specifically related to auto fuel.  More likely, the idle mixture adjustment on your carburetor has become too lean.  The symptom of a too lean carb idle mixture is backfiring or a slight popping for a brief moment when the throttle is reduced for landing.  If an extended glide from downwind to final is done, then the exhaust will pop slightly for an extended period.  The idle mixture is usually adjusted slightly when the ambient temperature moves from hot to cold, or vice versa.  It is not unusual to adjust the idle mixture periodically.  Your mechanic can adjust the mixture by turning the screw towards the label “R” for rich or “L” for lean.  However, adjusting the idle mixture may affect the idle.  So, the idle rpm setting, which is a separate adjustment, may need to be checked.

Here is a link to a short description of setting the idle mixture and idle adjustment:  http://www.sacskyranch.com/eng135.htm

Here is a link to an article on the Marvel Schebler carburetor which illustrates the idle mixture screw:  http://www.kellyaerospace.com/articles/Accessory_AMT.pdf

Harry

Oil Sump Stud Loose

I have a Continental 0-200 in my 1976 Cessna 150M with 5350TT and 1760hrs SMOH. The engine runs strong and the compressions are all in the high 70's. I had a problem where the Carb Heat cable nibbled a small hole in the bottom of the oil pan and caused a slight oil leak. I removed the oil pan and had the hole braised by a professional. I then reinstalled the oil pan and when I did a run up, one of the studs that hold the oil pan on, fell out. I cleaned out the hole, used high strength threadlock on the stud, let it set up overnight, and re-installed but could not get it to tighten. What are the alternatives. I can still see threads in the hole with a mirror and bright light. Does it have to be heli-coiled, or can it be re-tapped and a larger diameter stud used? Any info would be appreciated.

I don’t think that there is an oversize stud available for the oil sump studs.  Oversize studs are common for the exhaust studs, but I can’t find anything but a standard part number for the oil sump studs. The typical repair would be to install a helicoil, which, as you already know, would require that the sump be removed to accomplish the repair.  Lots of work, but this will clearly solve the problem

There are some “form a thread” products to be found which are kind of an epoxy filler which forms some threads.  However, this might be as much work as pulling the sump and installing a helicoil.

Harry

Follow-Up

Thanks for your response Harry. My A&P came up with an idea of using a bolt rather than a stud. The bolt was threaded the same as the stud thread and was slightly longer. The bolt installed fine and tightened enough to stop the leak.

Duhh, I should have that of this!  Actually, a very practical fix for the problem.  I will add this fix to the knowledge base.

Harry


More Horsepower from a C90

I have a question for my C90-12F.The overhaul time is coming and i would like to have some more 10 to 15 Hp from my C90-12F.I hear that make a change from C90 pistons engines to C85 pistons engine without modyfying cam,etc...just raise the compression ratio to have more power with(i hope)a same or better torque and 10-15 more hp.

The C-90 and O-200 are nearly identical except that the C-90 is rated at 90 hp at 2475 rpm and the O-200 is 100 at 2750 rpm.   For an easy horsepower boost, re-prop the aircraft so that the engine can turn to 2750 rpm.  Of course, if the aircraft is type certificated, this is not a legal change.  Here is a link to the C-90/O-200 type Certificate which details the displacement, compression ratios, and rpm limits of the various engines:  http://150cessna.tripod.com/e252tcds.pdf.  Also, consult your Continental parts and overhaul manual and compare the parts breakdown between the C-90 and O-200 and you will find that these engines are virtually part for part identical.

For experimental use in non Type Certificated engines, C-85 pistons have been installed to up the compression ratio from the stock 7:1 to a whopping 7.8:1.  This mod yields a few horsepower, maybe on the order of five to eight extra ponies.  Nobody really knows for sure because modified engines rarely, if ever, are actually tested on a calibrated dyno under controlled circumstances.  The best guess, though, is that maybe an extra five horsepower can be achieved.

However, the C-85 pistons are not a simple drop-in change.  The outer diameter of the piston crown can interfere and contact the top of the combustion chamber of the cylinder.  The shape and dimensions of the combustion chamber vary a bit from cylinder to cylinder and the accumulation of carbon deposits can also affect tolerances.  I am told that a good starting point is to chamfer the C-85 piston with a 45 degree, ¼” wide band around the OD of the piston crown.  It may be necessary to cut by trial and error to get the fit right.
 
 There is a discussion group which has much more information about modifying the four cylinder Continental engines.  Go to http://groups.yahoo.com/group/Q-200_Engine_Group/ and sign up to get access to the information there.
 
Harry

O-200 Temperature Limits

I just finished a Zenith CH-750.  Cruise speed is 75-85 mph with a 36 degree wood prop (76").  I am running temps of 388 to 430 degrees on my Continental 0200-B.  One A&P tells me that's way too hot, another says 425 if normal.  I don't want to ruin an engine.  What is your valued opinion?

Oil pressure is 40 psi and oil temp is 190.  I'm running AeroShell 100 in it.  It's a 1965 0200 with 133 hrs since new.

Here is a link directly to the O-200B spec page at the Teledyne Continental website:  http://www.tcmlink.com/EngSpecSheetDocs/O200B.pdf

Max recommended CHT at cruise is 420F with a max CHT of 525F.  The 420F is expressed as “recommended” but not as a hard limit.  I would interpret this to mean that your engine is very close to the range of tolerances, running just a bit on the warm side, but not alarmingly so.  I’m fairly certain that you could tinker with cooling air and get the temps back into a nominal range.

Most of the Zenith cowlings I have seen have just an open hole for cooling outlet in the bottom rear of the cowling.  If you look at a cowling installed on an Aeronca 7AC Champ, you will see a bit of a lip or deflector which extends downwards in the same general cooling air outlet on the cowling.  This lip acts like a spoiler and creates a bit of low pressure just at the cooling air exhaust cutout in the cowling.  The low to high pressure differential helps to scavenge out the cooling air and invariably lowers engine temps.  I’m going to throw the ball back to you, but if you do some research in Sport Aviation, EAA Experimenter, and KitPlanes, you will find numerous articles on adding a deflector to improve cooling airflow through the engine.  Even if you tape a simple deflector in place, I wouldn’t be surprised if your temperatures drop.

Harry

Follow-Up

Wanted to report that a salty ole Continental factory tech asked for the CHT's and corresponding EGT's.  He noticed that the hottest CHT had the lowest EGT and told me I had a valve "on bankers hours; opening late, closing early".  I drove to Tulsa, bought a .030 over push rod, installed it on the exhaust valve and lowered the temp by 30 degrees.  I still have cowling issues we're working on but the four cylinders are now at least in range of each other.

Interesting!  This makes sense- if the exhaust gas is not released from the cylinder, then CHT will go up due to convective heating from the hot gasses being retained in the combustion chamber for a longer period of time.  If not enough time is allowed for the gasses to exit, then the exhaust valve side won’t heat up due to reduced time exposure to  convective heating.  We kind of focused on the cooling airflow and didn’t really consider the heat producing and pumping aspect of the engine.  Good info- thanks for the feedback!  This troubleshooting experience will definitely go into the archive.

Harry

Follow-Up #2

Well the prototype CH750 from the factory in Mexico, Mo. just left after three days of testing.  We now have the same cowling, the same baffling, the same everything.  The only difference is: their 0200 is a 2008 and mine is a 1965.  Theirs has over 550 hours on it, mine has 153 since new.  We used the same CHT probes on the same day and theirs runs almost 100 degrees cooler.  So we're no further along than we were.  Do I change the cylinders?  or could it be the cam?  The change out of the push rod in #2 brought it down about 30 degrees but it still reached 456 degrees on climbout and this is in a 798 lb. airplane.  I'm just stumped and so is everyone else who has been involved with this project.

Given the age of your engine, you certainly have the old O-200 cylinders which are affected by FAA AD 96-12-06.  Continental also has published Service Bulletins MSB94-8C which has some details on O-200 magneto to engine timing:  http://www.tcmlink.com/pdf2/MSB94-8C.pdf

In summary, older O-200 engines fitted with older style cylinders require that the timing be changed from 28 BTDC to 24 degrees BTDC.  The retarded timing has the effect of lowering cylinder head temperatures.  The AD required the timing change to reduce cylinder head cracking, which has the implication that the cylinders ran hot at the original advance setting.  I think that if you compare older cylinders to newer cylinders, there are subtle differences in the cooling fin arrangement.  For example, more cooling fin area on newer cylinders.

So, I would change the timing to 24 degrees and see if the temperatures drop.  And if the temps don’t drop, then work on the next step.  Maybe boroscope a cylinder to look for rust, or something obvious in the cylinder bore.  However, the cylinders can be removed and re-installed in a day (or maybe a weekend for the first timer).


Harry


Modified C-75 Vibration at Low RPM

I have a C-75 that was modified with an O-200 crank, rods and jugs. It runs well but shakes below 1200 rpm. I have checked the carb and all the intake system for leaks and it checks out. I have been timing the engine to the values for the C-75 (28 and 30 deg). A fellow told me to set the timing for the C-90 (24 and 26 deg) and now it idles well down to 800-900 rpm. I see that the O-200 uses 24 deg on both mags. Perhaps this will improve my idle more, but I don't know if those numbers are appropriate to the C-75 cam, which is what I assume I have. What should the timing be on one of these hybride engines?

As you are finding, once an engine is modified from a stock configuration, it becomes somewhat of a guessing game to figure out how to make it work.  I specifically limit my answers to stock configurations as there is known data to work from.  When an engine becomes modified, the data points become increasingly variable.

As far as timing your modified engine, I have no idea what the correct setting will be.  You have built an experimental engine, so it is time to experiment!  The range of four cylinder magneto timing is 24 to 30 degrees BTDC.  Incrementally set the timing at these various points to see which yields the best results.

In regards to the rough idle, if you are using a primer, make sure that the primer is not leaking fuel into the intake.  Leaking primers can cause rough running at idle, accompanied by sooty spark plugs.  Disconnect the primer from the intake and cap off the port with a rubber cap,  Also, the carb venturi size and jet sizes may affect the idle and full rpm operation.  Once again, because your engine is modified, this will take some experimenting with different parts to sort out.

Try different timing settings first, though.  This is relatively simple and doesn’t cost anything except for time.

Harry

Converting from Fuel Injection to Carburetor

Of interest to me is a C-85 fj for an L-16 project. The present owner claims the ExCello FI system is newly overhauled, which I take as not necessarily true as no new parts have been available for decades. Besides removing the ExCello unit and plugging the intake manifold fuel line holes what else would be required to use a carburator with that engine? Which carburator would you prefer for reliability? Thank you.

If you want to convert from the fuel injection to a carbureted engine, I can’t really find a Continental Service Bulletin on this topic.  The Engine Overhaul and Parts manual will provide the specific parts requirements.  A quick and dirty list would include the following:
  • Carb (the least expensive is the Stromberg, although the Marvel Schebler has a bit more control over the mixture and somewhat better parts availability.  Either carb works the same if properly overhauled).
  • Intake spider
  • Intake elbows (or properly cap the injector leads on the existing elbows.  In the long run, it is probably easier to buy different parts)
  • Airbox ( the FJ unit is completely different)
  • Air filter (also different than FJ unit)
  • Add carb heat control (maybe have to change throttle linkage)
  • Cover for pad where injector pump mounts
  • Various hardware

The conversion would also require an FAA form 337 to be submitted and approved to document the change from one engine model to another.  In this case, the engine would be changed from a -8FJ to a -8F.  If the seller tries to argue that the engine data plate can be stamped to a different dash number with no approval, he is incorrect.  There are old Continental Service Bulletins which imply that this can be done, but those old service bulletins are obsolete and have been superseded.  The current FAA requirements require a form 337 be approved to document the changes to keep the engine legal.  Period.

Regarding the Ex-Cell-O, this unit can provide good service if overhauled properly.  However, impulse coupled magnetos are a virtual necessity as the Ex-Cell-O has a reputation for being tough to start when it is hot.  Impulse mags help this situation a bit.

Harry


On Overhauls

[Harry also provided the information below in response to the above question - RJW]

The terms “overhaul” and “rebuilt” are not clearly understood by most buyers.  The OEM is the ONLY entity which can legally use the term “rebuilt”.  The term “overhaul” is applied to a device worked on by an FAA licensed shop or person outside of the OEM.  However, within the term “overhaul” there is a range of tolerances from factory new to service limits.  So, the Ex-Cell-O injector can be termed “overhauled” but the tolerances can be all over the place.  The highest level of overhauled part would be one which is supplied with a Yellow Tag from a licensed repair station.  The lowest form of overhaul would be one line statement in a logbook, signed by an A&P, which states something to the effect of “…overhauled in accordance to manufacturer’s specifications…” with no other details.  Sometimes an unlicensed, amateur enthusiast will overhaul the part and a supervising A&P will sing off the work.  This is not entirely impractical as some restorers know much more about the device in question than a licensed mechanic.  Sometimes the enthusiast know very little and hoodwinks an A&P into signing off the work.  Engines on a pallet deemed to be “running when removed” or parts which were overhauled by an old mechanic who can’t be located result in problems more often than not.  I might sound pessimistic, but I have seen problems time and time again related to vague claims on running condition or the overhauled condition of parts.

So, when verifying the overhauled condition of a part, look for details like a sheet which provides the tolerances of the inspected and repaired parts or receipts for the work.  Sometimes you have to interview the mechanic who completed the repairs.  Be suspicious of any part lacking documentation or a firm connection to the person reported to have completed the work.  Ultimately, the part will be what it is, and the value is determined by how much of a chance the buyer is willing to take that the part is in the condition represented.

Here's a definition of overhaul terminology and standards which I found at the Mattituck engines website.

Engine Overhaul Terminology and Standards

TBO time draws near and you need to decide on a course of action. You call around, talk to your maintenance facility, and find that you are totally confused because you don't understand or know the definitions of many of the terms used by the people that you have been talking to.

New limits, Service limits, Remanufactured, Rebuilt, New, Used, Overhauled, Like new, OEM, Aftermarket, what does it all mean?

Lets look at and define the terms that are approved to be used by the FAA.

A NEW ENGINE is an engine that has been manufactured from all new parts and tested by an FAA approved manufacturer. The engine will have no operating history except for test cell time when received. No FAA approved manufacturer can approve another entity to manufacture or assemble a NEW ENGINE.

NEW LIMITS are the FAA approved fits and tolerances that a new engine is manufactured to. This may be accomplished using standard or approved undersized and oversized tolerances.

SERVICE LIMITS are the FAA approved allowable wear fits and tolerances that a new limit part may deteriorate to and still be a useable component. This may also be accomplished using standard and approved undersized and oversized tolerances.

An OVERHAULED ENGINE is an engine which has been disassembled, cleaned, inspected, repaired as necessary and tested using FAA approved procedures. The engine may be OVERHAULED to NEW LIMITS or SERVICE LIMITS and still be considered a FAA approved OVERHAUL. The engine's previous operating history is maintained and it is returned to you with zero time since major OVERHAUL and a total time since new that is the same as before the OVERHAUL.

A REBUILT ENGINE is an engine that has been OVERHAULED using new and used parts to NEW LIMITS by the manufacturer or an entity approved by the manufacturer. At the current time neither Teledyne Continental nor Textron Lycoming approve any other entity to REBUILD engines for them. The engine's previous operating history is eradicated and it comes to you with zero hours total time in service, even though the engine may have had used components installed that have many hours of previous operating history .  For years Textron Lycoming used the term Remanufactured in their advertising and commercial media to describe their factory rebuilt engines.   Around 2001, Lycoming discontinued the use of the term remanufactured and started using the term REBUILT to describe their factory rebuilt engines. So, prior to 2001 when Lycoming used the term Remanufactured to describe an engine, that engine should be considered to be a REBUILT engine

When an engine is OVERHAULED or REBUILT the new parts that are used during the repair process can come from a variety of sources. An O.E.M. part is a new part that is manufactured by the original engine manufacturer to stringent F.A.A. standards. An AFTERMARKET part is a new part that is manufactured by someone other than the original engine manufacturer that meets or exceeds the same stringent F.A.A. guidelines as a new O.E.M. part.

Any other terms used to describe the work performed during a engine overhaul are defined by the person or entity using them. They have no official meaning and often times are very misleading. Terms like "overhauled to factory specs or tolerances", "rebuilt equivalent", "overhauled to like new condition" and "remanufactured to factory fits and limits" and any other terminology that isn't defined above needs to be investigated as to what those terms actually mean. You will probably find that advertisements and log entries that use undefined terminology are not really delivering what you think you are getting. There are specific requirements by the FAA for the use of the terms OVERHAULED and REBUILT in an engine's maintenance records. If these requirements are not met it is illegal to use the terms. Any terms other than those listed have no meaning in the eyes of the FAA and should not be accepted by you in your engine log books.

Now that we understand all the terms, let's put it all in a nut shell. Only the manufacturer can currently produce a new or rebuilt engine. Both new and rebuilt engines are made to new limits. A new engine will have all new O.E.M. parts. A rebuilt engine can be produced using a combination of used and new O.E.M. parts. An overhauled engine can be done to new limits or to service limits or a combination of the two using used parts and new O.E.M or new aftermarket parts. An overhauled engine comes to you with its previous operating history intact and zero hours since major overhaul. A new or rebuilt engine comes to you with no previous operating history and zero hours time in service, even though, in the case of a rebuilt engine, some of the parts used may have a previous operating history.

Understanding these terms and the regulations that apply to them, may make the decisions that you have to make, at TBO time, a little easier.


O-300 Missing

I purchased a 1964 C-172E in February.  It has the 0-300D.  At that time it had 230 hrs. SMOH (rebuilt in 2004).  I have since put another 130 hours on it.  The oil has been changed every 25-30 hours.

Many 0-300 owners love their engines for how smooth running they are.  Sadly, that is not my case.

It has never ran perfectly.  It doesn't have a dead miss.  It is more of a da...da...............da.da....da........da..da...............da........................da..da......da.  type of thing.  I can hear it from the pilots seat and friends can hear it from the ground.  My problem seems to be gradually getting worse.  I don't think it is a safety of flight issue.  Several different instructors have ridden with me and haven't commented on it (maybe they don't want to hurt my feelings, I don't know).  It is more of an issue that "I know it isn't right".

About 50 hours ago, on initial cold start-up, it would start flawlessly and run smooth for 2-3 seconds, and would then roughen up with a slight vibration.  Mag checks don't isolate it. Carb heat RPM drop is normal.  Recently, it is just a little harder starting (20% harder) and runs rough from the beginning.  I have ran the last 3 tanks of fuel with 4oz.. MMO per 10 gal.  No change, yet.  I did a compression test and got 74-78 on all holes except left rear which was 62.  Air was escaping past the exhaust valve.  I pulled the spring and inspected.  About 40 degrees of the valve showed half as much seat contact as the rest of the valve.  I lapped the valve.  After clean up and running it, the compression rechecked at 72.  The valve felt good in the guide and didn't seem excessively loose.  I removed all of the plugs for inspection and cleaning.  They were all medium to dark grey on the electrodes and light to medium grey on the insulators except the left rear plugs which were yellowish on the insulators.  I bead-blasted and blew out the plugs and reinstalled (not in same holes).  I did not have them tested.

So, at this point I have good compression and probably good ignition (plugs, mags, wires).

From my understanding of your other responses, carburation wouldn't cause a problem throughout the RPM range.  What is left?  Sticky valves?  Valve lift?

Sticky valves.  If I pull each valve spring and slide each valve in and out by hand and it feels good, can I eliminate sticky valves?  Or, as the engine builds heat, will it bind a valve that felt smooth when it was cold?  I would like to know the answer to this even though my problem begins now at initial start-up.

Valve lift.  ?  I hope not.

The mechanics I have asked about this have hem-and-hawed around and finally said we could check this or that.  I really don't want to pay them while they are "learning" about Continentals.  So, I have come to you.  You have already "learned" Continentals and can cut to the chase.  Any response/direction you can give would be greatly appreciated.

I am not sure if this is related, but it may be more info for your diagnosis.  About 10 hours after purchase, while taxing, the RPM suddenly dropped about 250 RPM.  I thought I was imagining things until I did my idle check.  It was definately 250 lower than it ever was before.  As a newbie student, I took off anyway.  After the flight the idle was fine.  It did the same thing 50 hours later.  This time, I ran it up to 1600 RPM  and back to 1000 RPM a few times and it fixed itself.  It hasn't happened since.

P.S.  I always treat the engine/airplane gently, usually operate from 3000-5000 MSL, always lean the mixture, have only used 100LL, and use AeroShell 15-50.

Of course, there is no magic, one size-fits-all, answer for your problem.  But, I can suggest a couple of quick and dirty possibilities.  Keep in mind that these are just suggestions, and might be dead-ends.  I can’t accurately diagnose your engine without looking at it, so you should let your mechanic conduct some methodical diagnosis.   There are no shortcuts to diagnosing your problem, so I am not surprised by your mechanic’s hemming and hawing.  Like me, they can only guess until the can physically look at the engine.  Like I say, there is no magic answer.

However, I can offer some speculation.  Your comment that the engine has become progressively harder to start is a symptom often associated with a break, or “open”, in the windings of the secondary circuit of the magneto coil.  This can be a tough problem to isolate as the magneto will kind of run ok during a run-up check.  But, if the coil has an open, heat and therefore resistance increase the voltage demand at the gap of the open.  Eventually, the voltage demand will increase to point where the magneto cannot develop sufficient voltage to jump the gap of the open, and a certain percentage of sparks will not be generated and the spark plug will not fire.  The magneto is producing 2400 sparks per minute, so a couple of hundred missed sparks results as a slight roughness.  Since your engine is a six cylinder, the roughness is a bit less pronounced and more subtle than on a four cylinder engine.

But, as the open gap becomes wider, the voltage demand required to jump the gap increases until reaching a point where the magneto cannot develop enough voltage to jump the gap of the open.  The hard starting is an important clue to an open in the ignition coil.  The magneto is a poor producer of electrical energy at low rpm, so any condition which increases the demand for energy, such as an open, will deteriorate the magneto’s ability to produce energy.  The end result is the engine begins to start hard.  However, once the engine is running, the magneto can generate enough voltage to jump the open, and appear to operate normally, although maybe with a bit of roughness.  Eventually, the magneto will be unable to generate enough voltage to jump the open, and the magneto will apparently go suddenly dead.  In fact, the hard starting provided plenty of warning of a deteriorating problem.

My second quick and dirty guess is a sticking valve or lifter hydraulic unit.  Sticking valves are very common with the O-300 cylinder, but are very tough to diagnose until the valve becomes solidly stuck in the guide.  There will be some hints- fouled spark plugs, compression problems due to burned valve seats, but only very subtle indicators until a hard failure occurs.

The exhaust valve which you found with a burned seat is a good starting point.  If the valve sticks open then the valve seat burns.  It doesn’t take much interference from carbon or varnish on the guide to get the valve to stick.  Maybe the hydraulic lifter which opens that valve is malfunctioning.  At the minimum, you might want to have your mechanic ream the valve guide and conduct a leakdown inspection on the lifter hydraulic unit on that valve.

I don’t think that you want to put off having a professional look at your plane.  If your engine has a problem which can be detected from an observer on the ground, if you can hear and feel the problem in flight, and the condition seems to be getting worse, it just makes sense that the problem should be investigated further.

Harry

O-200 Cylinders on a C85

My mechanic has somehow lost the cylinders I gave him last winter to refurb, hone and re-ring (due to excessive blow by).  He has a set of refurbed O-200 pistons and Cylinders that he is willing to install on my C85 (on a 1941 Piper J-5A) if I can find and procure a STC to do it.  Do you know of any STC's that would cover the pistons and Cylinders only without changing the cam/crank and rods?  The engine has about 800 hours on the bottom end and the oil pressure is good and no metal in the oil screen so I an trying to keep from doing a rebuild on it for 300-400 more hours, even though it was put on the airplane in 1985.  If I can't find a STC we will have to find some good C-85 cylinders or see what kind of a deal the mechanic can give me on the rest of the O-200 he has in parts, assembled and installed on the J-5.  He would get my C-85 for when he finds the cylinders and I would get a big bill for the exchange and an extra 15 hp.  Thanks for any help you can give me.

Unfortunately, there is no STC for just O-200 cylinders.  However, the basic C-85 and O-200 cylinders are nearly identical, except for valve springs and minor details.  If you have a set of O-200 cylinders, you might want to see if you can have a cylinder shop convert the O-200 cylinders to a C-85 configuration.  If you do this, then there are no major changes to the engine.  Just bolt he cylinders onto the engine.

By the way, installing the O-200 crankshaft, rods and cylinders does not increase horsepower on a C-85.  If legally installed and legally run to the limits detailed by the STC, the parts change provides no increase in engine horsepower.  The increase in legal horsepower is an Internet wives tale or at least a continual re-telling of incorrect t information.

Yes, when the crank, rods, cylinders and piston are bolted the O-200 are bolted to the C-85, the C-85 becomes mechanically similar to the O-200 in crankshaft throw and displacement.  However, the C-85 is legally limited to 2575 rpm whereas the O-200 is rated at 100 hp at 2750 rpm.  The difference in rpm limits the modified C-85 to 85 hp.  I think that most customers report that the engine runs stronger, which is probably true.  But, if you think about it, the primary reason to convert to the O-200 parts is because the C-85 is runout and in need of a rebuild.  Of course, once the engine is rebuilt with any sort of new parts, the previous “tired” engine is going to feel like a “new” engine with lots of power.  Also, once someone has spent the money to convert their C-85, there is little chance that they will not say that the conversion yielded heaps of power.

So, it is an outright myth that a C-85 will be turned into an O-200 via the parts detailed in the STC.  A C-85 remains a C-85 if the STC is accomplished in a legal manner.

Harry

Replacing a C85 with an O-200

Thanks for the information.  I'm thinking more and more just see what kind of a deal he can make me on the O-200 that he has (he did a 150/150 taildragger and has the O-200 left over) assembled and installed on the cub.  What is the differance in the engine mounts on the C85 and the O-200?  I think the engine mount I have on the J-5 cub cruiser is the original one that was for the A75 that was on there in 1941-1985.  Are there adapters that could be fitter to use the original engine mount?  I know a few J-5A have O-200's and I can get 337's from them via "the cub club" it would be a good engine for the airplane (weight and balance and fuel burn wise).  Thanks again, I'll talk to my mechanic again and see if he has found them yet, he needs to get rid of some of his parts and wreaks he has in storage.

Now you have moved on to the next set of problems.  First, you will need to determine if the O-200 can be legally installed on the J-5.  The installation will probably require a different propeller to use the O-200 vs the C-85.  This is outside of my realm of knowledge, but the Cub Club will certainly have an answer.  www.cub.club.org  The FAA does not allow previously approved 337 data to be used for new 337 approvals.  You can use the existing 337 as a template for a new approval, but all of the approval process will be new for your airplane.  The best route would be to use an STC, if available.

Next, the O-200 and C-85 have different offsets on the engine case for mounting the engine to the airframe.  The C-85 uses a conical rubber mount which is cast into the rear portion of the crankcase and the O-200 uses a stack up of rubber pucks and washers.  The mount on the O-200 engine is case more forward than the C-85.  The O-200 would need some kind of spacer to set the engine forward to the same dimensions as the C-85.  Once again, the Cub Club would certainly have this answer.

Harry

Hydraulic Lifters

Harry, We are presently near completing restoration of long stored Aeronca 7AC N83996 and its Continental A-65-8 engine. On disassembly of the engine for inspection, all clearances were found to be well within limits for airworthiness. The engine was in good running condition when stored and would produce the normal static RPM required for the installed metal propeller. On disassembly of the engine, one of the eight hydraulic lifter assemblies (lash eliminator) was noticeably shorter in overall length (2.121 in) Vs the other 7 (2.480 in). A new lifter assembly was ordered for the A-65, on receipt it was also the shorter length (2.121) P/N 637269. My Continental overhaul  Manuel 1957 lists the part number as P/N 21609. but there is no way to ascertain what the installed 7 lifter P/N  are. what is the proper lifter P/N ? Are these two lifters  interchangeable? Obviously the shorter length was performing its function as it was flown without problems before being stored. Thanks for your generousity in help keeping the flying folks flying. 

The Continental hydraulic unit is common to the A-65, 75, 85, 90, O-200, C-125, C-145, O-300, and GO-300 engines.  The hydraulic units used in other Continental engines are of a completely different design and impossible to install in the smaller engines.

But, I did a little research and I find that the hydraulic unit has been superseded a number of times from one part number to another:  21609, 531694, 637269 to 646846.  I don’t have any details on what changes occurred, but the part number change implies some sort of mechanical or design change.  The engine overhaul manual does not list a dimension for the lifter assembly alone, but it does list a dry tappet clearance with the hydraulic unit fully deflated of .030” to .110”, or a total range of .080”.  The overall length difference between your two hydraulic units is .359”, which would appear to be too much difference if one just looks at the numbers.

BUT….

The Continental engine is subject to a wide range of tolerance variances and stack-ups.  The height of the cam lobe, the thickness of the face of the tappet body, the length of the pushrod, thickness of the rocker arm face, recession of the valve seat and valve mating surface and overall wear of these tolerances will all vary which will affect the “dry” valve to tappet clearance.  During operation, the hydraulic lifter pumps up from oil pressure, or inflates, and closes the gap to a zero clearance, or tight fit.  So, the engine can operate with a wide range of internal parts tolerance variance, so long as the dry tappet clearance falls within the specified range.  Pushrod length is sometimes varied from short to long to bring the valve lash within spec, too.

The hydraulic units are not stamped with part numbers, and there is no document which provides an overall dimension of these units.  A complication here is, that while the hydraulic units may apparently be mixed and matched so long as the dry lash gap is within specifications, there is the clear problem that older part numbers cannot be fitted to later engines.  But, newer part number units which supersede the older part numbers can be fitted to older engines- so long as the dry lash gap is correct.

So, a couple of different directions to go here.  You may want to assemble the engine with the various hydraulic units and measure the gaps in accordance with the overhaul manual.  If the gap works out, then you are in business.  If the gap doesn’t work out, then you can try undersize or oversize length pushrods to get the gap correct.  The engine may have been assembled like this previously, but if you didn’t keep all of the lifters, hydraulic units, pushrods, rocker arms and valves matched then the original assembly stack up has been lost and you have to start over to get it right.  You might have to juggle pushrods around to find the right balance of length.  Assembling with the existing parts is certainly the least expensive route.

Another method to approach this problem is to replace all of the lifters with the newer, shorter style of hydraulic unit.  But, these units are pricey, $75 or so at this writing, so it ads $600 or so to the overhaul.  Another variation is to contact Fresno Airparts or El Reno Aviation to see if they have any good used parts of the original design.  El Reno is very likely to know what the difference is between these parts.

When the dust settles, though, so long as the lifter holds pressure over the specified time during the leakdown check specified in the Continental manual (you did do the leakdown check, right?), and the assembled dry tappet clearance is within spec, then there is probably no problem with using various part number hydraulic units.  However, I’m not the guy signing the logbook, so the mechanic who will do the signoff will need to make that judgment.

 By the way, to clear my conscience and to perform my legal obligations as an FAA A&P, the most current manual for the A-65 is Continental Form X30008, dated August 1977.  You probably want to obtain one of these so that you can complete the overhaul legally using the latest approved data.

 Harry

C85 Intake Spider

Your name has come up as one to ask about this intake spider. I am looking for one for my C-85-12 with a Stromberg carb. I have found that there are 2 numbers. 35145 and 35145A1. Many people have said they are the same for C-75 through the 0-200. Univair however lists them both on their website and after inquiring, they told me one has an opening of 1 3/4" and the A1 has 1 7/8". In addition, there is $100.00 difference.

I have been asking around and the people that have them tell me they all have the 1 3/4 opening including the ones for the A-65. So now I am completely confused and was hoping you could point me in the right direction.

According to the Continental parts manual (you do have one- right?  I attached one just in case- the Univair catalog is not FAA approved data)  the 35145A1 is approved for all C75-12 through O-200 engines.  I have one of these in my hand and the bore measures to 1-7/8”.  The A-65 manifold, marked p/n 4780, has tapered venturi in the bore, but the large diameter is 1-3/4”.  The 35145 is probably a later part number to supersede the 4780.

Harry

TCM Oils and Lubes

Hi Harry, I own an Aeronca Champ 7AC with a continental A65-8F engine.The engine has 900 hrs SMOH. I only fly in warmer temps like 68-86 degs F. I am using 15w50 oil. How many hours between oil changes and is 20w50 oil OK ?    I live near Winnipeg, MB Canada,
 
Continental Service Instruction Letter SIL99-2A provides Continental’s approved lubrication listing and oil change