Which cylinders to use to top a P.Ponk engine?
My 1981 182R with P.Ponk engine is in annual now and we have one cylinder (#5) that has low compression. We have borescoped it and still looking at options -- it still might be save-able. We have ECi cylinders on this engine (IO-520C core), and they are subject to the ECi AD, where they need to be junked if taken off. (It is my understanding they cannot be overhauled and put back on.)
Question is what is your experience with different cylinders brands? I am looking at the Superior Millenium family primarily because of reputation, availability and cost. I cannot determine from the logbooks on whether my ECi cylinders have high- (8.5:1) or low-compression (7.5:1) pistons. The P.Ponk STC specifies the 7.5:1 pistons (again my understanding). The two cylinder part numbers I am looking at are SA52006-A22P (7.5:1 pistons) or the SA52006-A20P (8.5:1). I know you have to keep the same piston type if we just swap the one bad cylinder. But any down-sides to having one Millenium cylinder and the 5 remaining ECi? Or should I just bite the bullet and to a full top overhaul so all cylinders types match? I will probably hit the required 1000 hrs swap for the ECi cylinders in the next 1-1.5 years anyway. If I do the full swap, any reason to go with 8.5:1 vs 7.5:1 cylinders (besides the obvious mogas possibility with the 7.5:1.). I fly >95% "civilized" airports and 100LL availability is not a huge issue for me.
Any experience you can share, and any other cylinder recommendations you have would be greatly appreciated!
Comments
What is the compression numbers ? less than 30/80 ?
where is the air leaking ? Exhaust, rings/ crankcase, intake. ?
I leaking exhaust valve can be lapped to restore a good seal.
Compression for #5 was 8/80 - leaking exhaust valve. Borescope showed the damage exhaust valve.
These are ECi cylinders subject to the infamous AD. My understanding is that they cannot be removed and replaced, or even repaired in place.
With a burned exhaust valve, the cylinder has to be replaced.
Maybe contact the P.Ponk folks on the specifics of the cylinder.
Any manufacturer cylinder can be used, it just has to have the same compression ratio.
I think I have a path forward, after analysis of borescope images and many discussions with A&P and shops. Borescope of this cylinder does show the cresent shaped coloration and the starting of a green crescent on the exhaust valve. Talking with a reputable engine shop, they can built or match me a cylinder if I send them the old piston. I think I will go this route and get back in the air in a couple of weeks versus 2 months. A couple of other exhaust valves are showing early wear, so will lap and replace the rotocoil on those.
That sounds like a plan...good luck.!!