[snowman]

Do a leakdown or have it done for you. Engine does not have to be in car or be at operating temp. THe leakdown will identify the source of the low compression, ie valves or rings or both. Do the test and go from there.

THe problem you identified is a gross problem, ie low compression. Do not let the relatively small differences between a hot leakdown and a cold one prevent you from doing the test that will still tell you whats wrong with the engine.