[STEELCITYFIREBIRD]

Originally Posted by dataway

It would be weird if it ended up being something like the valley pan flexing under fluctuating vacuum signal ... like popping the bottom of a tin can back and forth.

I could only see that happening if there is no or inadequate source of air in to motor.

Just pull PCV valve and cover with your thumb. No noise reduction or smoother running... move along.

Compression tester is nothing more than an air pressure gauge with a check valve inline. (motor is an air pump your testing). A quick check with your shop air from a rubber tip blow gun will verify your gauge and integrity of the hose and check valve against shop compressor line regulator gauge psi output . The only thing you can't check is how well it will seal to the spark plug hole.(without some fabrication).

Any info/pictures on which crank pin/s the problem occurred on or pics of crank and damaged/replaced rods/parts?

Take all the spark plugs out when doing compression test on an entire engine!