How can a motor have 60-70 psi lower compression in 2 cylinders and then all the cylinders have 3-4 % leakage.

Bad can lobes/lifters?

Has to cam lobes,pushrod or something not letting valve open to get air in.

quote:

Originally posted by Wooley:
Bad can lobes/lifters?

Bingo. I would measure lift of PRs on all cylinder vs good cylinders...

Ok. So there seems to be an consensous here. So I will check.

Thanks for giving me a place to start

Before you get too far into it, try repeating the compression test on 6 and 8 again, with the throttle held wide open.

Yeah I am going to. The motor has gas ported pistons. the theory is since the motor sat over the winter that the rings may be stuck on those 2. Maybe when I put air in for the leakdown it popped the rings back out. Gonna look at it tonight

Are you doing these tests on a hot/warm engine?

warm

I haven't read this whole deal,,,

One question, is the motor running up to par or is it slow? If its running good forget about both compression and leak down testing!

If its off then you have an issue!

Its been so cold here in Maryland, havent run it yet. The main issue how this thread started was the vacuum pump filling up the overflow tank in a matter of minutes.

quote:

Originally posted by TOP38:
I haven't read this whole deal,,,

One question, is the motor running up to par or is it slow? If its running good forget about both compression and leak down testing!

If its off then you have an issue!