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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