Harry Fenton's Hints and Tips for Small Continental Engines

Updated 3 December 2011

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 Mayville, New 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 Visalia, CA 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 Victoria, Canada 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 Pueblo, CO.  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