I purchased a basket case..It dropped a valve on rear cylinder but engine was running. I replaced the heads and valves and I set the timing and adjusted the valve clearance. Afterwards, I did a compression test and on the front of which I did not touch and the compression was 180 lbs. The rear was 90 Lbs. Would it be that the rear cam is 180 degree off or what is the problem. I need assistance and my email is [email protected]. Please some help me on this. The cams are aftermarket so I am not alarmed at the 180 lbs on the front but on the back I am concerned. The top of the piston was chewed up a little and I did not replace it. Please get back to me.. Si.