Hi all. I have an 80 Camaro with a camel hump head 350 with flat top pistons which puts it around 9.5:1. With the valves set properly it only has 90-100 compression on every cylinder with a compression test with car warm, throttle open, and all plugs out. When I loosen the valves to the point where they clatter the compression test goes up to 150. Also putting oil in the cylinder makes the compression test go up to 150 as well. I am stumped because this low compression test is happening on every cylinder. What could be causing this? Any help would be greatly appreciated.

 

I set valves, yea I know, with engine at idle, and take the lash out by ear. Used to have a valve cover that was cut out in the center. I'd suggest revist the valve lash, as you say oil in the cylinder, you probably don't have a problem. Is there some particular reason to do a compression test?

 

That's exactly how we set these, at idle, by ear, 1/4 turn after tick was gone with cut out valve covers to keep oil at bay. I did a compression test because mid to top end power seemed a little short for what's been done to the car and I know 90-100 psi for a 9.5:1 compression motor is way too low.

 

If you're running 150 across the board, that's very good, squirt of oil doing a compression check is always what I'd do, that get's the rings "close" to operating condition as you can with them static.Look at carb, my sugestion

 

Every SBC I have ever owned ran 140-160 cold. Typically if you have to put oil in the cylinder to get compression to go up, there is usually a problem. But it's odd for it to happen on every cylinder as the issue I am having.