[Dale Campbell]

Has anyone had a valve stick open at high RPM on I/O 360 normally aspirated engine.
I have a valve that opens and closes fine at idle, but at high RPM my #4 on front engine sticks open. It happened just before annual and the mechanic did not get it solved. He added something to the oil and said it would free it up. It did for a few flights and now the problem is back. I have a Insight CHT/EGT and the #4 jug shows 350 degree and exhaust shows 1250 degree at idle. At normal flight 2500 RPM and above #4 head temp drops to 90 degree and exhaust reads 120 degree instead of normal 1350 degree like the rest. He changed all 12 spark plugs, check mags, compression is 78-LBs on all cylinders and cleaned fuel injector. I flew yesterday for 2 hours. The first hour all was good. I landed for fuel at Lock Haven,Pa. on climb out the #4 Jug failed to hold temp. and I could feel the little vibration of the miss firing. I flew for a half hour and it never came back on line until I pulled throttle back for landing. On the ground at idle all temperatures are ok. We are going to pull valve cover on #4 exhaust valve and check for broken valve spring and also move piston down and hammer on valve with rubber mallet to see if it solves my problem.