Correct Cranking Compression?

[Brian Mc]

could 100-115 lbs across the board cause a slight miss at low throttle a.k.a. no boost? I found stock valvesprings and 3 warped valves in a 114K engine. Should a 3 angle valve job and new springs take care of the skip? i tried all the ignition components and cleaning the injectors.

 

[Nick Micale]

Never seen that low a number for an '86-7, usually around 150#'s. My guess, assuming you have verified these numbers like using another know good gauge, is that your timing chain is worn really bad.

Stock valve springs will not show up like this, and warped valves would be much lower value than a "good" cylinder. How did you verify warped valves?

 

[Brian Mc]

Verified warped valves by grinding them, timing chain looks good, not stretched, but i guess i should probably replace it anyway. So 150# is the goal? thanks.

 

[tazgn]

I've seen 115# on mine before. But I didn't open the throttle blade while doing the check. When I opened the blade I get 165# on all cylinders. But I would think that if you're within the 10% rule between all the cylinders that it wouldn't be the valves. As those 3 valves would only affect those 3 cylinders. I can't think of anything being wrong with the motor that would cause ALL the cylinders to be low AND within 10% of eachother besdies maybe the cam being way off, clogged intake track (i.e. throttle not opened), or a bad compression tester. Just my ONE cent worth of knowledge.

Derrick

 

[Brian Mc]

Ok i didn't check it with the throttle open that may hae been the problem.

 

[S10xGN]

Didn't see your cam listed in sig, but remember - the overlap will affect cranking compression, too (i.e. more overlap, less cranking compression).