In article ,
test it wrote:

I have heard many people, including a couple of A&Ps, say that when
the rings on a cylinder all line up that the cylinder will loose
compression. This doesnt make sense to me because if the rings are
going to leak, then they would leak anyway. There is an air path
between each ring for the air to go.

The reason I am saying this is that my wifes RV-4 engine has a
cylinder that is reading 55 psi on the compression check. She was
advised to run it a few more hours and then recheck the compression
because the rings might all be lined up and be causing the low
compression.

What say the experts. Old wifes tale or not?

Regards,
Tom Velvick



Your best bet is to use your ears! If you hear air escaping (hissing)
at the exhaust pipe, your exhaust valve is leaking; if you hear it in
the intake manifold, intake valves are leaking; hearing it at the oil
filler indicates ring leakage.

A cracked cylinder head will sometimes have a draft at the crack, which
you can feel with your fingers.