Does this low stroke aero engine really need an overhaul? — General Aviation News
Question to Paul McBride, the General Aviation News engine specialist: I took my 1959 Cessna 182 in for its annual inspection and we found a low compression cylinder. After pulling the cylinder, my mechanic says the engine needs to be overhauled due to the condition of the cam and tappets. I replaced all the tappets four years ago. Why would weightlifters get stung? Looking at the camera, do you think it should be demolished?
The existing overhaul has 800 hours, but it was done in 1991. I bought the plane in 2016 with 120 overhaul hours.
Paul’s response: Mark’s problem is a good example of a common situation in the world today. And with the cost of avgas these days, we’re entering a time where more and more aircraft will be idle for long periods of time – and the results could be even worse than what Mark has seen here.
I hate to be the bearer of bad news, but from the photos and information you presented, I’d say if this was my engine, we’d be on the way to an engine overhaul.
Even with the information you provided, I have to read between the lines and try to use some common sense to give you the reasoning behind my answer. I think the most important thing is to look at chipping on the tappet faces and the same on the lobe of a cam.
If you cut your oil filter, I wouldn’t be surprised if you found metallic contamination. If there is no metallic contamination found, I would almost bet that if you keep running the engine you will see some soon.
It is for this reason that I recommend having the engine overhauled.
That’s not to say that simply replacing the tappets at this point won’t get you a few more flying hours out of this engine, but we do know contamination will continue, and that could lead to who knows what?
In the worst case, this could eventually lead to engine failure, depending on the amount of contamination.
The important thing to remember is this: we know the chipping started on both the lifters and the cam lobes. If you only replace the tappets, it won’t prevent the cam lobes from continuing to chip. Once a metal is moved over either part, there is no way to stop it if the engine is kept running. At some point, this can lead to contamination sufficient to damage other expensive parts, such as the crankshaft.
I realize you purchased the aircraft in 2016 with only 120 hours on it since major overhaul (SMOH). If we look at the overall picture here, we are talking about an engine that is 63 years old and has already undergone an overhaul as far as we know.
I guess we would find that there were a lot of long periods of inactivity for this aircraft. As I’ve mentioned many times in the past, pairing infrequent running with infrequent oil and filter changes puts us in the worst possible condition for an engine to go into an unpleasant state of internal corrosion. It’s a cold hard fact that infrequent operation and infrequent oil and filter changes shorten the life of any engine, and sadly, you see the results firsthand.
I realize this can all be a real blow to you, but the condition of an engine this old is not unusual. My best advice is to act now and have the engine overhauled.