LML Gang,

Doing the annual on my 320 this week.  Compression check shows 77-78 on cylinders 1, 2, 4.  #3 is 75 and I hear pretty good leakage through the exhaust, indicating a leaking exhaust valve.  I’ve had no indication of sticking valves or morning sickness.  I pulled the rocker cover and there is no abnormality there.  This engine is typically run lean of peak at power settings of 55-65% power.  Oil changes every 25-35hrs.  Engine has 623hrs since new.

My question to those of you who are much more experienced with the Lycoming 4-cylinder engines, is what should be my next course of action?

·         Do the valve lapping procedure per the Lyc service instruction?

·         Start using TCP and re-check in a few hours?

·         Go run the engine hard and re-check the compression?

·         Something else?

I really want to nip this in the bud and not end up with a burned exhaust valve, requiring pulling a jug.

Appreciate your thoughts and responses.

Cheers!

Dan Olsen