O-320 compression test
The early O-320 is a great engine. If it is an "H" model not so good(lousy camshafts). Above 60 you are "legal". If you are concerned screw in the tester,have a freind hold the prop for each cylinder and listen for the leakage at the oil filler, muffler and carb to determine what is the leak. (Muffler= exhaust valve,
oil filler= rings, carb= intake valve. If it's rings try a little oil spray in the plug hole and rock the prop for a better reading. If it's valves, remove rocker cover and hit the valve rocker with a SOFT mallet with the air on, and see if the compression
comes up. AT ALL TIMES MAKE SURE THE PROP IS HELD STATIONARY!
Install a new rocker cover gasket. Personally,I wouldn't worry too much unless the engine is over TBO.