REFLECTOR: Lycoming IO 360 C1C Valve Problem Question

Joel Smith joels at austin.rr.com
Tue May 15 10:50:54 CDT 2007


If you have experience/knowledge in this area, I would appreciate any 
ideas you have to offer.

Problem:
Cylinder #4 fails static compression test.   0/80#

Symptoms:
Engine warm up for a few minutes result in the compression test passing 
with good numbers. Engine usually starts rough and smooths out. We think 
it smooths as the valve gets happy.


Analysis:
Compression test cold reveals a very audible leak out the exhaust port. 
I dropped the exhaust stack to check the valve stem for build up that 
might be jamming in the valve guide. The valve cover was also removed 
for additional inspection. What I found is that the rocker arm is not 
being released to allow the valve to close. I can spin the valve with my 
finger (through the exhaust port) through a full 720 degree cycle. So I 
know the valve isn't closing. It should not spin when the valve is 
released onto the face. I tried to insert a .003" feeler gage in the 
tappet area, and as expected, to tight. I have not removed the rocker 
arm assembly yet to verify that I can get valve closure (got a bunch of 
stuff to remove... that's next).

As I understand it, this engine has hydraulic lifters. The only thing 
that I can think of that would cause this is a stuck lifter (some 
how...), maybe a push rod being to long (however it gets longer with a 
warm up, not shorter....)....

Any ideas?

Additional Info:
Engine has less that 100 hrs since rebuild.

Thanks,
Joel



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