AFAIK if you change any of
then the cylinder needs to be re-honed and a new piston and rings fitted. This is because the new combination won’t “bed-in” unless you have a fresh hone (the criss-cross pattern).
In fairly rare cases they pull off a cylinder and put it straight back on, with nothing touched, and that is ok.
You now need to follow the Lyco bedding-in procedure (including the correct oil and without camguard). The first few hours of it are particularly critical.
Excellent news on the bottom end. It’s great to have that data point. It can be done without pulling cylinders but very few people know that.
Re the future, always fly at peak EGT, going to “best power” (c. 150F ROP; typical EGT there is about 1350F) only during climb.
Great news on the camshaft etc. Sounds like, as long as you keep flying regularly, with the odd cylinder, the engine has years of safe flying left in it.
Thanks for posting all of the photos and the ending – a good educational thread for me.
Pardon the dumb questions, but is the small/coloured valve the exhaust valve? Is the size difference consistent across engine types/manufacturers? I.e. when boroscoping, how does one know which valve is input and which is exhaust?
I understand that one can tell whether a leak is rings or valve by listening during propellor rotation. However, knowing that it is a valve, looking at the photos above, it isn’t obvious to me which valve is the one that’s leaking. Suggestions?
In our typical aero engines, the smaller one is the exhaust valve.
