Hello,

I just want to share a recent experience with my 2007 O-200 A82 engine.  While flying in the pattern at my home airport (KMCC) it started running rough with somewhat reduced power.  We immediately landed and taxied back to the hangar.  We pulled the top spark plugs and did a quick compression test and found that the #3 cylinder had no compression.  I had an A&P look at it and he found that the #3 cylinder had two intake valve rocker arms instead of one intake and one exhaust and the exhaust valve outer spring was broken.  The intake valve rocker arms don't have the oil orifice for valve stem lubrication so they weren't getting lubed properly.  That apparently caused the spring to get overheated to the point where it failed.  The engine has only 350 hours on it so this is definitely a premature failure.

I did some research and found a couple service bulletins that would have provided an opportunity to catch this problem if they had been performed during annual inspections.  The most applicable one is M77-19 (http://www.tcmlink.com/pdf2/M77-19.pdf) which identifies the intake and exhaust rocker arms.  The other one is SB08-1 (http://www.tcmlink.com/pdf2/SB08-1.pdf) which calls for inspecting the rocker shaft.

My particular engine had been sent to Ly-Con Aircraft Engines in July 2010 (just outside of warranty) to repair a galled lifter so I don't know if the engine had the incorrect rocker arms when it was new or if they messed them up at Ly-Con.  Also, the #1 and #4 cylinders have two exhaust valve lifters.  The only cylinder that has the correct intake and exhaust valve rockers is #2.  It seems likely that it came from Continental that way since I've heard of others having similar problems around that timeframe.

I looked at the EMS data and noticed that the #3 cylinder has been running 30-50 degrees hotter than the others even though it is in front of the engine and should get better cooling.  The data doesn't go back very far so I don't know how long it's been like that.