Advice on Engine Overhaul Risk for Low Time Infrequently Used Engine

Hi all,

I need some advice based on your experiences with O-360 C4P or similar engines. I am looking at a low time aircraft engine but it is about 10 years old and only has about 200 hours. The first 140 hours were when it was first purchased and flow that year and then the next 8-9 years it only had 60 hours put on it. Lycoming says the TBO is 2000 hours or 12 years which will be in two more years. The engine was in dry country in a heated hanger and had an annual every year with oil change. It did not have the Lycoming recommended "long storage" procedures applied (spraying special oil in through the spark plug holes and cycling the prop to coat the cylinder walls). I have heard stories of many of these low time engines getting run 25-50 hours and then the seals blowing or bearings going and you end up with a $20-30K bill.

Lycoming Service Instruction No. 1009AT excerpt note below
“Engine deterioration in the form of corrosion (rust) and the drying out and hardening of
composition materials such as gaskets, seals, flexible hoses and fuel pump diaphragms can occur if an
engine is out of service for an extended period of time. Due to the loss of a protective oil film after an
extended period of inactivity, abnormal wear on soft metal bearing surfaces can occur during engine
start. Therefore, all engines that do not accumulate the hourly period of time between overhauls
specified in this publication are recommended to be overhauled in the twelfth year.”

Have any of you folks had experience with this?

If I get an engine oil analysis done and it comes back clean is it only the seals that are at risk?

Any comments and advice would be appreciated.

Since a Lycoming cam sits high in the engine the biggest potential problem will be a rusty cam. In fact it's likely there's some rust. The only way to find out is to pull a cylinder or two, which also will give you the opportunity to see how the cylinders have fared. The engine may be a peach or it may be a pit.

Since it had an annual every year, did the IA run it up? My IO-360 engine had been in a crate in my heated shop for 40 years before I put it in my Cub. I could not find any rust on it in places which were exposed, mags were off, or looking inside the cylinders through the spark plug holes. I had the fuel injection system overhauled and installed P-mags. So far it has flown 50 hours and runs like a top with no oil leaks.

I just experienced a similar thing last year, and I ended up overhauling it. Cam is the weak part. Boroscope it before you buy and negotiate from there. That is what I did. I tried to seat rusty cylinders, did not work and ultimately threw in the towel. Fortunately because of the scope, I was able to buy the airplane right so I could cover my butt.

Overhaul risk low, Iran risk High. figure a teardown and cam/lifter recondition before you ruin it all and need an overhaul at 300 hrs.

It will probably have rust in it. When you first start it up (or run it) that rust acts like lapping compound. It does not just disappear. That rust accelerates the wear on internals but it may not wear evenly. You may wear out the cyl walls, rings, valve guides, main bearings, cam, cam followers, oil pump, etc. All or any weird combination of the above. As mentioned the cam is the most likely suspect, but pouring sand/lapping compound down a running engine is not conducive to longevity. Thus engines that have sat for a long time are a crapshoot. You can't really predict what will wear out, but the odds are something will, long before TBO, thus resulting in an early overhaul.

My opinion only

Bill

I am just finishing up a rebuild with a similar background. The engine sat for 25 years in the desert. We tore down the engine and there was no rust on anything, we were amazed how good everything looked after all that time. With that said we did an overhaul, more for peace of mind. It was a good thing we did, the prop flange had a crack in it from a prop strike that was not in the logs or disclosed. With that said I would at least pull the cylinders and look at the crank and cam.

My 2 cents worth is to pull the cylinders and have a look inside. If it is clean then I would do a top end overhaul and go fly. Thats what I did and got 600+ hours out of my C-90 that was last overhauled in the mid eighties.

I 2nd S2D above..... There is a difference in Lycoming vs. Cont. .... Cont.'s(sometimes) seem to be somewhat like a Briggs & Stratton, I've got a 3.5hp B&S that's 40 years old that's had the oil changed maybe 3 times and goes on like the Ever ready bunny. Have seen several small Cont's treated the same that just keep going too...... Cam is major concern on Lycoming. I'm in the middle of a decision myself. I have a 1700 SMOH IO320 B1A that's going into my AcroDuster2. It was running well when the plane(twin Comanche) was hit with a big AD and older owner parted it out. Guy I got it from purchased it for a spare intending to rebuild but he too is older and decided to bail out..... It had excellent care. 3 cylinders 200 since new and other rebuilt at same time. Crank etc. all standard.....If not for the fact that it sat for a few years, I'd start it up and expect to get several 100 hours out of it. Indeed more than I would expect to fly a sport biplane in the time I have left(I'm an old dinosaur myself).... But that's a bad idea IMO. Likely(maybe) to have cam/lifter spalling from rust...running metal thru engine making future, hopefully "cheap"/standard, overhaul problematic. So I guess I'll pull the cylinders and take a look? If rusty, IRAN is the way to go......I can't afford overhaul, if necessary I'll replace/grind? cam etc. , button it up and hope for a couple 100 hours.... I might be able to just run it for as long as I will need it but why ruin a good well maintained(except for sitting) engine....? YMMV Jack

I have torn down 50 year old engine that have sat with no rust and 2 year old engines with rust. It is a crap shoot. Oil analysis might show something. Remove one or two cylinders to be sure. If you borescope the cylinders and they are clean your worse case scenario would be dissassembly and cam and lifter replacement. $6-8K. I have a feeling I am going to see that airplane shortly.

All, Thanks much for all the advice, we will have the front cylinders pulled to take a look and the guessing will be over.

Steve Pierce said:

I have torn down 50 year old engine that have sat with no rust and 2 year old engines with rust. It is a crap shoot. Oil analysis might show something. Remove one or two cylinders to be sure. If you borescope the cylinders and they are clean your worse case scenario would be dissassembly and cam and lifter replacement. $6-8K. I have a feeling I am going to see that airplane shortly.

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Steve, you must be able to see into the future.......

And don't forget SB 505........if it applies:sad:

OregonCub said:

Steve, you must be able to see into the future.......

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Been talking to the current owner on this subject prior to his purchase. I told him to listen to his wife, put Bushwheels on it and keep it.

OregonCub said:

All, Thanks much for all the advice, we will have the front cylinders pulled to take a look and the guessing will be over.

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The guessing wont be over. They can still have the beginnings of corrosion on the cam and lifters, and it won't show up for a while. I've seen a couple carefully inspected by competent engine guys still eat a cam.

plan on buying a cam, and if it doesn't happen, you've got more gas money.

MTV

I say buy it expecting to overhaul it. I bought a J-3 with a C-90 6 years ago that had 357 hours SMOH in 1989. Short story, ran it 20 plus hours with no oil leaks, clean plugs, cylinders, but burning a quart of oil every 4 hours and continued to slowly lose power. After 30 hours, tore down Tuesday to find trashed cam and rust in all cylinders. Nothing that $$$ won't fix.

Pat

I pulled a cylinder and inspected the suspect engine. She was clean as a whistle, no sign of any corrosion. I was able to put my borescope into the next cavity in the crankcase and inspect some of the rear lifters as well and they were all clean. The cylinders were clean as well. I have inspected engines with a light rust where you can see exactly where the piston was sitting when the engine was inactive. No such marks in this one. The airplane was in south west OK in a heated hanger and that was probably a contributing factor. Another reason I like the airplanes out of the southwest.

Sweet! Thanks for the pictures and the report.

Wow, great photos. Thanks

Bill

OregonCub said:

All, Thanks much for all the advice, we will have the front cylinders pulled to take a look and the guessing will be over.

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Pull both cylinders from one side.

That way you can see all lobes of the cam, not just the front ones...

Flew it home from KGCM to OR65 over 2-1/2 days and the engine ran like a top. Had Tailwinds the whole way with 11K Density Altitude at KSAF, dodged
T-Storms after KPGA to KEKO and then fuel at KBNO to OR65. Will try to post a few pictures once I resize and assemble them.

n40ff said:

I 2nd S2D above..... There is a difference in Lycoming vs. Cont. .... Cont.'s(sometimes) seem to be somewhat like a Briggs & Stratton, I've got a 3.5hp B&S that's 40 years old that's had the oil changed maybe 3 times and goes on like the Ever ready bunny. Have seen several small Cont's treated the same that just keep going too...... Cam is major concern on Lycoming. I'm in the middle of a decision myself. I have a 1700 SMOH IO320 B1A that's going into my AcroDuster2. It was running well when the plane(twin Comanche) was hit with a big AD and older owner parted it out. Guy I got it from purchased it for a spare intending to rebuild but he too is older and decided to bail out..... It had excellent care. 3 cylinders 200 since new and other rebuilt at same time. Crank etc. all standard.....If not for the fact that it sat for a few years, I'd start it up and expect to get several 100 hours out of it. Indeed more than I would expect to fly a sport biplane in the time I have left(I'm an old dinosaur myself).... But that's a bad idea IMO. Likely(maybe) to have cam/lifter spalling from rust...running metal thru engine making future, hopefully "cheap"/standard, overhaul problematic. So I guess I'll pull the cylinders and take a look? If rusty, IRAN is the way to go......I can't afford overhaul, if necessary I'll replace/grind? cam etc. , button it up and hope for a couple 100 hours.... I might be able to just run it for as long as I will need it but why ruin a good well maintained(except for sitting) engine....? YMMV Jack

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Well since I made my "do you feel lucky" comment on the other recent thread I might as well give you an updater on the above engine. I ended-up pulling all 4 cylinders to make inspection and re-torque easier. I found the cam & tappets clean although the cylinder bores were rusted. Some rings were stuck so I replaced all rings, honed and re-assembled. The engine runs like a top, good compression and oil pressure. I changed oil at 23 hours(after install in the Acroduster 2) and found some metal and carbon. Ran it another 10 hours and changed oil and then again and its still making metal. Sent in a sample of both oil and metal and they say it's probably the cam and tappets. Anyway at least I've finished flying off the 40 hour phase 1 but I guess I was NOT lucky. As soon as the weather gets better I'll take the engine apart......

Oh well

Jack

I built an O-320 for my Dad's Clipper and an O-470 for a C-180 on the field at the same time. Took the parts to AEA in Dallas to save shipping to Tulsa. My Dad gets the engine hung, flies it to Alaska and back. First oil change back he has some steel in the screen. We send it off and it is such and such material. Call Lycoming and they say cam and follower material. He pulls the engine, brings it down here and he pulls it apart and the cam and followers are fine. Call Lycoming and ask what else is such and such, they say rod and rockers. Come to find out the rockers weren't ground square and the valve tip was chipping off this steel. AEA said they reset the machine for each set which I though sounded fishy. Pulled the O-470 rockers and they had the same issue just not nearly as much time.

n40ff said:

Well since I made my "do you feel lucky" comment on the other recent thread I might as well give you an updater on the above engine. I ended-up pulling all 4 cylinders to make inspection and re-torque easier. I found the cam & tappets clean although the cylinder bores were rusted. Some rings were stuck so I replaced all rings, honed and re-assembled. The engine runs like a top, good compression and oil pressure. I changed oil at 23 hours(after install in the Acroduster 2) and found some metal and carbon. Ran it another 10 hours and changed oil and then again and its still making metal. Sent in a sample of both oil and metal and they say it's probably the cam and tappets. Anyway at least I've finished flying off the 40 hour phase 1 but I guess I was NOT lucky. As soon as the weather gets better I'll take the engine apart......

Oh well

Jack

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Any chance you could comment on any changes you noted like trending lower static RPM or even were you noticing "softer" pull through on the prop during the 10-20 hours you have run it? What I am thinking is a real measure of cam condition or trends could perhaps be measured by "dynamic compression" tests instead of static tests as we do normally. It wouldn't show up in an engine that has been sitting at first but would show the trend so you know what is coming. I have torn down two engines with bad cams and only one gave any indication there was a problem, a 172 that a customer flew in was complaining about low power. My boss took it around the pattern and it just didn't have any power. Static compression was fine but two lobes were flat enough to be quite obvious. We did not do a dynamic test before tear down. The other was a C150 Continental and it ran fine. The lobes had slight spalling in a couple of spots. It was timed out was the reason for the tear down. No other indications.

Because this "sitting" business is such a problem and a crap shoot it would be nice to at least have some way of knowing it's coming after a few hours running. Maybe catch it before it ruins the bearings. On the two I have torn down the bearings and other parts were fine as far as could be seen and I don't remember any problems from the re-conditioners of the parts so if they had been low time engines I think new cam and followers would have saved the day at that point.

I thought I read somewhere that oil analysis wasn't a good predictor of cam problems? It surprised me but I thought the source reliable at the time?

Engine runs strong. If anything a new vibration. Other than that you would not think anything is wrong. Indeed in an open cockpit bipe I would have paid no attention to the vibration except that it's new.... Oil analysis was indeed fine, it was the particles/pieces of metal that are the bother.