Compression readings

The air in the cylinder test is a simple one. Although too many people just use maximum shop air and expect to find it, a lot of times, full shop pressure is too much and can throw off where it's actually coming from, so here's how I do it. I regulate the air down to 10PSI and do the test on each cylinder.

Air out the exhaust pipe is burned or improperly seating exhaust valve, ir something keeping it open. Maybe a guide too tight.

Air out the intake manifold at the carburetor mount pad, same thing with an intake valve.

Air coming up into the valve cover/rocker arm area will be bad or broken rings, hole in a piston or "some such".

Regulating the air pressure is important, as it will help you pinpoint the problem faster.

I agree with Jim. You shouldn't have any air coming past valves under any circumstances. The rings however, will have a little leakage, but not bad.