[Jac Mac]

Leakdowns are expressed in percentage points. Since you used 60# to test you should multiply all results by 1.666666 to get % numbers.

eg 60 x 1.66666=Approx 100lb/100%
Therefore your 55# = 91% & 50# =83%

Head gasket coolant leaks wont show high % numbers , but any individual cyl that cause cooling system pressure requires further investigation.

When checking cyls try to bring piston up in direction of rotation to TDC, you can get variation in readings if piston is rocked at TDC. Also doesnt hurt to re-test at BDC with valves closed, only way you will find cracked cyl walls etc.

Should have added that you therefore have 9% leakdown on the 'good' cyls & 17% on that bad one.