Most knowledgeable mechanics understand that engine compression means very little, while most laymen place some degree of stockin it it as a symbol of engine health.
Well Blackhand must fall into the category of UNknowledgeable mechanic because I understand that compression is very important to piston engine performance ( Health).
With smaller piston engines, both automotive and aircraft, one can feel the relative compressions between cylinders by rotating the engine by hand and feeling the relative effort for each compression stroke. Identifying which cylinder is down is another matter.
Radial engines of course have there own characteristics which would probably prevent one from feeling the compressions, SN3 could probably explain this better than me if he wasn't being so anal.
Cheers
Blackhand