Possible Causes for High-to-Moderate Cylinder Leakage
The cause of low pressure can be determined by listening for escaping air.* Air escaping from crankcase breather, dipstick tube, or sump plug hole: Defective rings or worn cylinder walls

* Air escaping from carburetor: Defective intake valve

* Air escaping from exhaust system: Defective exhaust valve

* Air bubbles in radiator or air escaping from adjacent spark plug hole: Leaking head gasket or crack in block or head Courtesy of Proform

SOURCE
Proform/Specialty Auto Parts
P.O. Box 306, Dept. SRM
Roseville
MI  48066