Let's say there is an O360A1A on a desirable plane, but it hasn't been flown much in recent history. 625 hours since 2002, 80 hours since 2011. That's 60 hrs/year 2002-2011, 10hrs/year since then. This time was exclusively in the summer, and it sat not flying every winter in Fairbanks. It was never pickled.

We can boroscope the cylinders easily enough to see if there's rust in there. And the seller says he's okay with a mechanic pulling a cylinder to look inside the case. Is that sufficient in people's minds for determining if the engine is trash from sitting? The engine was factory new 625 hours ago. Are there other places that need to be looked at on the engine? I realize the cam is the main thing (I think) but hoping to get a little more insight into what else to look at.

Thanks
-asa

You could also pull a mag and check the gears in the accessory case through that hole. Between that and what you see with a cylinder pulled I'd be pretty happy.

Look all you like, but that engine is almost certainly going to need a cam and followers. That won’t happen right away, of course, but it’ll happen.
So, you buy it with the understanding you’re going to have to buy a cam and followers.

Make your offer predicated on that expense. If he won’t sell for that price, walk.

Seriously. I can’t tell you how many of these ive seen.....

MTV

Mike, if it is confirmed by inspection that there is no rust on the cam and lifters or elsewhere in the engine at the time the buyer purchases the engine why should the seller be responsible for the need of a repair in the future (discounted price to cover repair). You are saying that every engine that has low rates of utilization over the years should have a reduced price because some have failures from corrosion yet by inspection the buyer has determined to his satisfaction that no corrosion exist in this particular engine at the time of purchase. That is the same as expecting the seller to warranty that the engine will reach TBO without any problem. As a seller if no rust was found and you still wanted to reduce the price do to the utilization rate I would tell you to hit the road, the engine(aircraft) was no longer for sale to you. To be honest when I price an airplane I am selling I take into consideration the chance of corrosion based on rate of utilization. I understand that the buyer is taking a risk, if the buyer wants to pull a cylinder to look inside the engine, my actual selling price will be higher as I am now assuming the risk that there may be corrosion. Now if I have flown the airplane for a couple of hundred hours in the last two or three years and it is not making metal, I really don't care how many hours it was flown per year prior to that. If the cam and lifters had rust, there would be metal in the filter within a couple of hundred hours, no metal, no problem. Just the opinion of one pilot, mechanic, aircraft owner who has bought and sold a few aircraft over the years.

Tim

Tim,

I hear you. The problem is that frankly, visual inspections aren't a perfect tool to positively evaluate corrosion in the internals of an engine. I've seen engines opened up by competent mechanics, inspected and a couple years later, started making metal, and the cam and followers were gone.

You can do what you want, and you can advise what you believe. I simply posted what I would do. Do whatever makes you happy, I could care less. But, in a year or two, I'd hate to hear that the gent is buying a cam and followers that he already paid for.

So, here's a question: Suppose you inspect that engine for him. Pull a cylinder, and visually inspect "everything" (which by the way is impossible in this context). Would you be willing to offer the guy buying the thing a solid warranty that if the cam shits itself in two years, you'll pay for a new cam, new followers, and the labor to install?

Like they say, opinions are like assholes: We've all got one, but the only one that doesn't stink is mine.

In this case, I've seen a couple of friends burned, even after supposed "due diligence".

FWIW, which may not be much. I wouldn't touch the thing without a serious discount.

MTV

I went through a similar 'look-see' at a very nice 180 HP Super Cub last summer. The plane was a near perfect example of perfection other then the engine had only been run 14 (maybe it was 16 hrs) in the past decade+!!! TT on the plane since new everything being basically a build up from a data plate with only the best oparts used. The owner had 'started it and ran it' for a few minutes every month during the summer. He did have a guy fly it with him aboard for a couple of hours just before I went to look at it.

Being concerned about corrosion, I contacted a well know and respected engine guru in the area. He suggested I remove the rocker covers as a first step and check for any corrosion on them. If there was much on them he suggested that the inside might possibly be corroded also. I was also told that the owners flying it after sitting that much mave have done a lot of internal damage that might not be noticed for 50-100 hours. I did as suggested and there was a fair amount of corrosion on the covers. The engine guru mentioned that I would be best off pulling the cylinders and having an oil analysis done. He quoted me $5,000-15,000 for tear down and refinishing the parts. The $15K was for a total refreshing of all parts and new rings/gaskets, etc.

The additional costs weren't in my budget so I walked.

Mike, in your sample, no I would not warranty the cam and lifters and labor because I have no control over what the guy does with it after he buys it. There is no benefit to me to unless the airplane is overpriced in the first place and this is the only potential buyer. If the buyer is still not willing to accept it then I would just use the inspection and photos to make it easier to sell the airplane at my price to someone else. As for corrosion in engines, it is any ones guess, last week an IA friend of mine showed me photos of rust pitting on a O470U cam and lifters with 400 plus or minus hours since overhaul two years ago. That airplane lives in their healed hangar year round at 60* or warmer, he has no idea why this has happened. Not making any metal yet but it probably will at some point. He also told me that his previous employer was having cam failures on IO360 Lycomings at the 1000 hour point flying a 1000 hours an year with 50 hour oil changes. My friend suggested that they change to 35 hour oil changes and the cams have been making it to TBO (2000 hours). Life is full of risk, if in any specific case the risk exceeds an individual's comfort level then they should not take the risk. If you feel that an airplane has an engine that has to much risk for your comfort level just pass but don't expect the seller to reduce the price to eliminate the risk. Or if I am the seller I will replace the engine with a fresh overhaul and just raise the price if you like, just give me a substantial deposit so I know you won't change your mind. Like I said before you will get a better price if you take part of the risk, lower risk to the buyer equals higher price.

wwhunter, Oil analysis in the type of case you described can indicate a problem when there may not be one. A friend of mine had a 170A with an O300 he was selling. The buyer wanted an oil analysis so my friend flew the airplane for two or three hours since it had been setting for a couple of months then changed the oil and took a sample. It had steel cylinders and was setting in Houston, so as you may have guessed there was some rust on the cylinder walls. This rust showed up as iron in the analysis so the recommendation was to fly it for 25 hours and test again, this went through three test then fly as recommended cycles before the analysis showed a normal iron level. Bore scoping the cylinders showed no rust pitting and the engine never had any metal in the filters, also changed at 25 hours. Oh, and you guessed it the buyer lost interest during the two months it took for this to happen. Unfortunately my friend had not required a deposit before the analysis. He did enjoy the flying though.

Tim

Tim

All good suggestions. There's some places to look for corrosion and premature wear. In my two experiences cam and lifter failure was first indicated by wear metals too small to filter, but may be seen with a bright flashlight in the drain oil as a silvery sheen or picked up with a magnet left in the sump oil. Soon the filtered chunks appear and the greens are planted and start growing to be exchanged.

Valve covers for internal corrosion, valves and guides for wear, borescope of the cylinder walls and valves, accessory case openings for corrosion all good to check. Removing the oil sump can allow access to the cam chamber via the narrow drain slots below the crankshaft in Lycomings, but pulling cylinders will offer a direct view. Cam lobes tend to flatten and develop a sharp edge at the nose that can be felt.

There's lots of pics about how the parts should look when used but still airworthy. Here's one source: https://www.cessnaflyer.org/maintenance ... -wear.html

Some sage advice on use: https://www.lycoming.com/content/low-ti ... -and-value Regardless of the TT

Gary

I put an oh 0-360 and stc from pen yan . 15 yrs ago flown lots year round .6 years and about 800 hrs started losing power checked cam gone . Pulled motor stripped 3 ex lobes half worn down. Other lobes perfect.sent data plate to Bart at aero sport built all new parts Block has roller cam.pen yan used a used cam on rebuild .complained they redid my clyinders and supplled me new cam part no I wanted all the other parts to reassemble put it together put in ex bushmaster.runs strong to this day.i just did a 0-320 160 last winter used the new diamound coated lifters .expensive I would not used reconditioned parts or used.that pen yan had lots of blow by .if any engine has excessfive blow by puts lots of moisture in crank case.long storage change oil run a bit leave alown .do not start every month for 5 mins.puts moisture in oil .use nickel clyinders

Why is this not an issue with automobile engines?

It is a problem in automotive engines that sit extended periods.
Not exactly the same cam Problem but pretty close.

AKclimber wrote:Why is this not an issue with automobile engines?

Aircraft engines are air-cooled and the internal working tolerances are loose. Water-cooled engines can be built tighter. Most automobile engines quickly recycle and eat their own combustion byproducts that get by the piston rings and valve guides then enter the crankcase. And they are also more closed to the atmosphere compared to aircraft that can inhale moisture with daily temp and humidity changes through open their breather line.

Another factor is oil. Aircraft oil is simple tech (think home owner's common 3-in-One oil) and most aren't formulated to prevent corrosion and control pH/acids that build up from combustion. Anything that can create ash deposits and stick exhaust valves is eliminated. There are aftermarket elixirs like Camguard that can be added to improve the oil's qualities, and some of today's low ash Diesel oils formulated to work with their emission components might perform ok.

Gary

Thanks Gary,
Are the auto engines tighter because of the thermal variability is lower than air cooled?
And the auto engines have oil breathers with a check valve in them, so why can’t aircraft use that too?
Seems to me that the air intake and exhaust are more or less the same, and the oil breather is the only other way to get damp air inside. Then the higher tolerances require different oil which allows the moisture to persist in the crankcase.

Does anybody check cam function at the rocker arms? It seems like you could easily use a dial indicator to verify each lobe but I haven’t heard of this being done. Any thoughts?

That's a very good idea, it would certainly show gross failure of a cam lobe. The problem is that it would NOT show corrosion or spalling on the cam oft follower face until it was bad enough to actually make the travel decrease. So, this technique would tell you that a cam or follower HAS failed but not that one is going to fail.

AKclimber wrote:Thanks Gary,
Are the auto engines tighter because of the thermal variability is lower than air cooled?
And the auto engines have oil breathers with a check valve in them, so why can’t aircraft use that too?
Seems to me that the air intake and exhaust are more or less the same, and the oil breather is the only other way to get damp air inside. Then the higher tolerances require different oil which allows the moisture to persist in the crankcase.

Yes dimensions primarily driven by thermal variability are lower in jacked water cooled engines.

A modern PCV valving system can require two components....a check valve you note (passive or electrical switched) to pass the combustion products and a filtered air source to replace them in the engine. I'm amazed some Green Group hasn't complained to the EPA about aircraft with loose bowels dumping on public land and water. Some motorcycles like Harleys can be modified with a catch can for the drool versus reburning it via the intake throttle body.

As an eye opener remove the oil filler cap or dipstick after flight and observe/smell the escaping gunk. If the oil filler is high enough air will enter the breather tube and stove pipe out the exit. In winter water vapor in the engine from combustion can be seen rising for example.

Gary

This is why I actually prefer to purchase a runout engine when I buy a plane. The owner knows the engine value is nil, and I don't have to negotiate from a point of different views of whether the engine is a risk or not. And as the buyer, I know going in that I am dealing with a likely engine overhaul or replacement, and any extra hours I get out of the engine before it starts showing signs of wear are just bonus hours.

Corrosion internally in an engine and what it may do down the road is rather a complex problem. For one, corrosion cells at a micro level are hard to detect until they become large enough to start lifting the plating. Corrosion can be accelerated by flying in a corrosive environment, take LA for example, high sulphide levels in the atmosphere. Then there is fuels.

I once sat next to one of the senior lubrication engineers from Shell coming back from London. Over the 8 hours sitting, we talked about oils. Oils are such a religious concept with many owners I rarely discuss it. It like talking to Vegans. The point he made is that most modern oils work about the same for the 50 hour change cycle. Where they fail is not from the total ability to lubricate, but their ability to disperse blow-by. He said the formulation of modern fuels to achieve octane rating without lead leads to an acidification of the oils. Diesel oil have buffers in them to keep the pH stable, but gasoline oil not so.

So if you previous owner was an auto gas enthusiast, you may have more corrosion due to that factor than the sitting alone. There are so many factors that influence the outcome, like the initial alloy, plating process and so on that can ultimately affect the metal's ability to keep it from corroding it is just nearly impossible to predict. Like the other poster, I like run-out engines. I know what I started with after it is overhauled. However, looking for bits of chrome plating in the screen is the usual indication of a cam breaking down from corrosion.

When I bought my Maule it had 90 hours on the Lycoming 235. It had set for 5 years only getting started at annual. My pre buy mechanic said it all looked good but said it could have some minute corrosion which could cause a problem later.

Well, 900 hours later it ate the cam. If I was buying a plane with an engine that had set for years not pickled, I would get a very big discount or walk away.

But, to each their own.

Cheers...Rob

Similar experience to Rob's. Plane sat 5 years, about 275hrs since overhaul on Lycoming O-540, mechanic pulled a jug and what we saw looked good. 350hrs later cam gave up the ghost.