O-360 Cylinder Pitting

[tfb]

Looking at buying a 500hr TT plane that’s 30 years old with an O-360. It’s been sitting most of the last 20 years. Pre buy scope confirmed pitting in the cylinders, though it still has excellent compressions for now. Obviously can’t see the cam or lifters but presume they are also corroded. I am trying to determine if the plane is still worth it, whether with some focused maintenance or straight to a major overhaul.

Does it hurt to fly with pitted cylinders as long as compressions are good and it doesn’t burn excessive oil? As long as they aren’t shedding metal that gets run through the rest of the engine? Or should I plan on overhauling/replacing them sooner than later?

Assuming the cam and lifters are corroded, could it make sense to IRAN them without majoring the whole engine? If the rest of the engine is in good shape, a major would only be resetting the clock 500 hours so I don't know if a major is as good of a value as a higher time engine. If so, would it make sense to do this before flying much to keep metal from getting run through the engine?

Talking with the pre buy IA he recommended to fly it as is with 25hr oil changes until it started making metal, but that was with the assumption you were planning the major. However, if it could make sense to not overhaul, I’m wondering if it’d be better not to fly it yet, and what you would want done before you did.

Thanks for your help.

 

[Grum.Man]

The pitting in the cylinders would be the least of my concerns. As long as the oil burn and compressions are acceptable to lycoming specifications you can fly it. My concern would be the crank condition. Severe pitting can cause a bearing to spin starving the engine of oil and causing catastrophic engine failure. Everyone has their own levels of caution when it comes to things like this. I personally would want to pull a cylinder to at least assess the internal condition. Whether you IRAN it or overhaul it will likely be determined by what you see when you open up the engine. If it's just a matter of overhauling the cylinders and maybe a few new lifters or cam then IRAN makes sense. If you see pitting on the crank and gears then it might be more sensible to do a full overhaul.

 

[Klaus M]

If you can't afford to overhaul the engine then you can't afford the aircraft. Let someone with money buy the plane and overhaul the engine. The rust from the cylinders is now in the engine sump waiting to be sucked up by the oil pump and grind the pump walls away. Very common see it often on engines over 20 years since overhaul.

I'm so confused why so many pilots want to challenge fate. The engine is dead. If it was in you wife's car you would replace the engine or the whole car. If a commercial flying service did something like flying passengers around in a corroded engine they'd be sued and FAA would take their commercial certificate. Good news is, your wife can sue Lycoming after your engine quits. Obviously, it's Lycoming's fault that the engine quit after sitting 20 years.

 

[Racerx]

I am trying to determine if the plane is still worth it

Maybe...it depends. Depends on what plane. What the ask is. A 30 year old plane is pretty new. But 30 year old rubbers are not. An overhaul is a somewhat known. But everything else that comes from disuse isn't. Hangared or sit on the ramp?

Pitting is rust. Pitting cylinders are one thing. Pitted cams/crank is another. Pitting cam leads to spalling in short order. If you're assuming the cam and lifters are corroded and you know the cylinders are corroded, I don't think it makes much sense to go IRAN vs overhaul. Now, if it's just the cylinders and cam is OK, then I'd IRAN.

 

[tfb]

I have not come across much about corrosion in the crankshaft, although a quick search showed some ADs for fixed pitch props. FWIW this one has a constant speed. It did have new hoses firewall forward, new carb, a new mag fairly recently. It otherwise looks new. It is in a non-climate controlled hangar in the midwest.

I am more trying to determine how much to negotiate. The owner thinks you can fly it for awhile and then do some IRAN, I am wanting to price in the complete overhaul now. I don't think we are far off, so trying to figure out if I can get some hours on it before tearing it apart.

 

[MRC01]

The O-360 cam sits on top, so it hasn't had any protecting oil for a long time, exposing it to years of corrosion. Most likely the cam is toast. Replacing the cam requires splitting the case, so you might as well overhaul the engine.

 

[Grum.Man]

I have not come across much about corrosion in the crankshaft, although a quick search showed some ADs for fixed pitch props. FWIW this one has a constant speed. It did have new hoses firewall forward, new carb, a new mag fairly recently. It otherwise looks new. It is in a non-climate controlled hangar in the midwest.

I am more trying to determine how much to negotiate. The owner thinks you can fly it for awhile and then do some IRAN, I am wanting to price in the complete overhaul now. I don't think we are far off, so trying to figure out if I can get some hours on it before tearing it apart.

The crank corrosion you should be concerned with is between the journal and bearing, not internal. The engine is three times it's recommended tbo based on years. If you have to drop 40-50k into an engine rebuild could you sell it for your total investment when done? What does your mechanic say? If he will not sign off on it and you have no other options you will be doing a top overhaul. Again, your own risk assessment will determine if you fly it as is or not. Mid west VFR with a bunch of fields and roads to land on, sure take the chance. Do you really want a plane badly enough to risk you and your passengers lives? How much are other ones listed for with newer engines?

 

[Racerx]

A corroded crankshaft is toast regardless if it's fixed or constant.

 

[chemgeek]

In a Lycoming, the cam and lifters are at the top of the engine, and are prone to corrosion, leading to spalling and cam lobe wear, if not operated on a regular basis. The case has to be split to remove the lifters and cam. Once you do that, you might as well evaluate the crank, and at that point, the labor involved pretty much makes a full overhaul the preferred option. If the lifters and cam are corroded, they will spall if not already, then the engine is on very borrowed time. Been there done that. When I found a spalled lifter and worm cam lobes during a potential cylinder replacement at 1800 hours and 20 years of calendar time (including the prior owner), I also discovered an out-of-tolerance crank while the case was split. That's how overhauls happen. Rather than do an IRAN for another few hundred hours, I just went full OH and zero-timed the engine. Years of inactivity, whenever they happen, shorten the lifespan of the engine.

 

[MRC01]

... When I found a spalled lifter and worm cam lobes during a potential cylinder replacement ... I also discovered an out-of-tolerance crank while the case was split. That's how overhauls happen. ...

Same thing happened to me in 2017. Cylinder had low compression. We pulled the jug, happened to see the cam with light corrosion. One thing leads to another... I opted for the Penn Yan O-360 upgrade, since I was going to overhaul it anyway, might as well spend a few extra bucks and enhance airplane capability.

Back to the OP question - that engine is almost certainly not airworthy. And that's assuming a dead engine is the only problem - sitting that long, who knows what other problems lurk within? It could also have structural airframe corrosion. If the seller won't deduct at least $30k from the price I'd walk away and find another airplane.

 

[Bell206]

Talking with the pre buy IA he recommended to fly it as is with 25hr oil changes until it started making metal,

Is this the A&P/IA who will be maintaining your aircraft for you after you purchase one? If not, his opinion is not binding. Perhaps ask him if he would sign off the engine is serviceable in the logbook?

 

[tfb]

I believe the currently negotiated price plus an overhaul puts it on the upper end of market value. That is compared to other low time engines but there is nothing to say they haven't been sitting either and would carry some risks themselves. A warrantied zero time engine would probably be preferable even with a little premium. However, that also puts it pretty close in price to the newer models with a higher gross weight and newer avionics. Those newer models have been listed for awhile though with price drops which makes me wonder if I shouldn't bide my time if the market may be softening.

I know the consensus is generally if you split the case, you might as well overhaul the engine since it is a better value. My motivation for this thread was whether that might not be the case here since this one has 500 hours. If I can IRAN for $10-20k and fly it, could that be a better value than spending $40k to reset the SMOH which to me means you're adding $10k in value (500 hrs current/2000 hrs TBO = 1/4; 1/4 x $40k for OH = $10k). Of course, that's assuming the rest of the engine is okay which is optimistic.

The plane was already pretty discounted and after the corrosion was found he offered it a little lower. I guess I was hoping to have found a deal on a plane but I need to determine whether I want to pay market or move along assuming the seller won't budge anymore.

 

[tfb]

Perhaps ask him if he would sign off the engine is serviceable in the logbook?

It is another IA in the area. I don't have a mechanic yet but have considered continuing to take it to the current shop since they already know it, or now since I know this guy that did the pre-buy, using him. The implication was that it was airworthy, though perhaps I should ask that directly.

If the seller won't deduct at least $30k from the price I'd walk away and find another airplane.

I think that's about where it is currently. I just need to decide if it's the plane I want at market price and accept it isn't the good deal it initially appeared.

A corroded crankshaft is toast regardless if it's fixed or constant.

Understood, I was more curious about the susceptibility of these engines. Even if I don't buy this plane, all the models I am looking at will have a Lycoming. I haven't seen much about the crankshaft corroding and was wondering if I missed something in my research.

 

[douglas393]

I believe the currently negotiated price plus an overhaul puts it on the upper end of market value. That is compared to other low time engines but there is nothing to say they haven't been sitting either and would carry some risks themselves. A warrantied zero time engine would probably be preferable even with a little premium. However, that also puts it pretty close in price to the newer models with a higher gross weight and newer avionics. Those newer models have been listed for awhile though with price drops which makes me wonder if I shouldn't bide my time if the market may be softening.

I know the consensus is generally if you split the case, you might as well overhaul the engine since it is a better value. My motivation for this thread was whether that might not be the case here since this one has 500 hours. If I can IRAN for $10-20k and fly it, could that be a better value than spending $40k to reset the SMOH which to me means you're adding $10k in value (500 hrs current/2000 hrs TBO = 1/4; 1/4 x $40k for OH = $10k). Of course, that's assuming the rest of the engine is okay which is optimistic.

The plane was already pretty discounted and after the corrosion was found he offered it a little lower. I guess I was hoping to have found a deal on a plane but I need to determine whether I want to pay market or move along assuming the seller won't budge anymore.

I would walk away. How much is your life worth when it turns out your mechanic is wrong, and the engine quits at the wrong time. There are plenty of planes out there and you are already questioning whether this plane is a good choice. Some may disagree with me but if you are questioning the airworthiness of the plane and are not sure it is worth spending whatever you need to make it airworthy it is time to look for a different plane. My experience has also been to multiply whatever you are told it is going to cost and how much time it is going to take by 1.5 and consider yourself lucky if it is not more than that.

Also remember you are not buying the plane as an investment, you are buying it for a mode of transportation or a hobby. It you are buying it as an investment I would suggest there are much better and safer ways to invest your money.

 

[rotormatic1]

I read a lot of posts about Lyc. Engines and corrosion. In the mid 70’s I worked at a shop that overhauled Franklin and Lyc. Engines in southern CA. Had a flatbed trailer out back that had around 50 timed out VO-435’s. They were sealed up with no special preservation oil. When taken apart, no corrosion. I wonder if the changes to engine oil thru the years is affecting corrosion if an engine is inactive. The old engines used straight 50 weight oil..

 

[Grum.Man]

I believe the currently negotiated price plus an overhaul puts it on the upper end of market value. That is compared to other low time engines but there is nothing to say they haven't been sitting either and would carry some risks themselves. A warrantied zero time engine would probably be preferable even with a little premium. However, that also puts it pretty close in price to the newer models with a higher gross weight and newer avionics. Those newer models have been listed for awhile though with price drops which makes me wonder if I shouldn't bide my time if the market may be softening.

I know the consensus is generally if you split the case, you might as well overhaul the engine since it is a better value. My motivation for this thread was whether that might not be the case here since this one has 500 hours. If I can IRAN for $10-20k and fly it, could that be a better value than spending $40k to reset the SMOH which to me means you're adding $10k in value (500 hrs current/2000 hrs TBO = 1/4; 1/4 x $40k for OH = $10k). Of course, that's assuming the rest of the engine is okay which is optimistic.

The plane was already pretty discounted and after the corrosion was found he offered it a little lower. I guess I was hoping to have found a deal on a plane but I need to determine whether I want to pay market or move along assuming the seller won't budge anymore.

The engine on it is worth maybe $6500 if you are lucky. While it only has 500 hours of a 2000 hour TBO it is 30+ years old on a 12 year TBO. If you price it in hopes of an IRAN vs an overhaul you are in for disappointment.

 

[mondtster]

In my experience, almost all Lycomings without plated bores will end up with some pitting during their lifetime. The real question is, how bad is it?

 

[mondtster]

I read a lot of posts about Lyc. Engines and corrosion. In the mid 70’s I worked at a shop that overhauled Franklin and Lyc. Engines in southern CA. Had a flatbed trailer out back that had around 50 timed out VO-435’s. They were sealed up with no special preservation oil. When taken apart, no corrosion. I wonder if the changes to engine oil thru the years is affecting corrosion if an engine is inactive. The old engines used straight 50 weight oil..

I’ve been suspicious that changes to the fuel is causing the increased corrosion rates we’ve seen in recent years.

 

[Bell206]

I don't have a mechanic yet but have considered continuing to take it to the current shop since they already know it, or now since I know this guy that did the pre-buy, using him.

I'm a big proponent of selecting your mechanic before you purchase an aircraft. But if you are looking to use someone previously involved with the aircraft or with this prebuy then talk to/question them as though they work for you now. Things have been known to change once the owners do or pre-buy opinions are different than what it discussed during your 1st annual with the aircraft. Good luck.

 

[Klaus M]

The plane was already pretty discounted and after the corrosion was found he offered it a little lower. I guess I was hoping to have found a deal on a plane but I need to determine whether I want to pay market or move along assuming the seller won't budge anymore.

tfb, you're experiencing something that is very common these days. The generation that the media calls "Baby Boomers" owns the greatest percentage of the privately owned aircraft. As they are faced with the big decision of getting out of aviation they don't want to give up easy. They want market value until the end. Many of these folks have waited long enough that it's now the estates problem to sell the plane. If you look around you'll find more and more of these aircraft that the estate will except most any offer. Good luck on your aircraft search but, don't push your luck with aged aircraft. Most all these aircraft need a very thorough teardown.

Air Power Inc. is a good place to look at factory pricing. Quite often the factory won't charge for failed crankshaft and case halves.

Aircraft Parts Supplier | Shop Small Aircraft Engines, Parts & Supplies - Air Power Inc.

Air Power Inc. is the largest and leading aircraft parts supplier online. We power the dreams of aviation pilots by distributing airplane engines, parts and supplies worldwide. Shop our aircraft parts supply store, and get back to soaring the sky!

www.airpowerinc.com

 

[tfb]

Thanks all. While it certainly is discounted I do not think the seller is completely pricing in the new engine plus the headache and downtime that comes with it. I agree it is a bad idea to fly it as is without further inspection. I will see if they will come down anymore and if not keep I will move onto the next one.

The real question is, how bad is it?

I plan to talk to the pre buy mechanic again this week, and that was one of the questions I had. He did not express much concern about the cylinders themselves and was more using them as a probable indicator of cam/lifter condition.

I'm a big proponent of selecting your mechanic before you purchase an aircraft.

I have heard that too but have been moving around with more moves to come, so it is not practical at this point. I talked to the current and independent mechanic and both shared the concerns discussed in this thread.

 

[Racerx]

500 hours means nothing in this instance unless the engine was pickled. It wasn't. So to compare it even remotely close to similarly timed engines is foolish.

Curious what model of plane this is. Most models that have a higher gross weight have about the same useful.

 

[Dan Thomas]

I read a lot of posts about Lyc. Engines and corrosion. In the mid 70’s I worked at a shop that overhauled Franklin and Lyc. Engines in southern CA. Had a flatbed trailer out back that had around 50 timed out VO-435’s. They were sealed up with no special preservation oil. When taken apart, no corrosion. I wonder if the changes to engine oil thru the years is affecting corrosion if an engine is inactive. The old engines used straight 50 weight oil..

Yes. Engines that were flown immediately before removal, no ground-running, will look clean like that. It's ground-running that does the most corrosion damage, by pumping a lot of water vapor past the rings then the engine is relatively cold and clearances are large. That moisture condenses in the case and starts corrosion. It gets boiled off harmlessly when the airplane is flown and the oil temps are in the normal operating range, but if that engine is just ground-run and put away, even if it's right after an oil change, corrosion is imminent.

I have seen this too often. I'd see pitting in the cylinders, and I'd ask the owner if he was ground-running it without flying it, and the answer was yes. It is not a car with their liquid-cooled engines and therefore tighter clearances, and with their PCV systems that scavenge the blowby from the case. Can't operate it like a car. Can't expect long life out of it if you do.

 

[mondtster]

Yes. Engines that were flown immediately before removal, no ground-running, will look clean like that. It's ground-running that does the most corrosion damage, by pumping a lot of water vapor past the rings then the engine is relatively cold and clearances are large. That moisture condenses in the case and starts corrosion. It gets boiled off harmlessly when the airplane is flown and the oil temps are in the normal operating range, but if that engine is just ground-run and put away, even if it's right after an oil change, corrosion is imminent.

I have seen this too often. I'd see pitting in the cylinders, and I'd ask the owner if he was ground-running it without flying it, and the answer was yes. It is not a car with their liquid-cooled engines and therefore tighter clearances, and with their PCV systems that scavenge the blowby from the case. Can't operate it like a car. Can't expect long life out of it if you do.

Ground running is not the only reason an engine will have rust in it. I’ve overhauled far too many rusty engines that simply flew 25-50 hours a year and were parked between flights with no care given to them. The engine that now resides on my personal aircraft is a prime example of the opposite of your suggestion - engine was on a .gov aircraft flying 200+ hours each year and serviced with an open checkbook. It was retired at TBO, where it was taken in on trade for an engine conversion. My engine sat for several years, unpreserved and in one of the most favorable climates in the US. The cylinders were so rusted and pitted that plating them is the only thing that will save them at this point. The rest of the engine was absolutely spotless however.

Car engines will do it too. Leave them alone long enough and you might find that it is locked up when you come back to try and resurrect it.

 

[bkspero]

I apologize if this has been covered in this thread of notes, but my skimming didn't catch it, so, here goes.

The discussion so far has focused on the OP's engine question. But airframe issues are also more likely in an airplane that's been in storage for many years. And the consequences of airborne airframe failure due to hidden corrosion are serious. And the cost of corrosion mitigation can be high.