Harry Fenton's Hints and Tips for Small Continental Engines

Harry Fenton works for Unison Industries.  He's 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.

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.

Subject Areas:

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

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.

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

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   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! :)


[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.


[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.


[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.


[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.



[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.

[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.


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.


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.


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.


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.


[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]

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