I will give as brief as possible description of the history of this problem and what is currently making me scratch my head. Awhile back my thermostat stuck on my 350 chevy I had rebuilt about 20000 miles ago it is not stock but had been a daily driver. The thermostat stuck and overheated my truck I shut it down as soon as I noticed it was getting hot, I removed the thermostat and it imediately cooled off and I drove it home. I thought the problem was fixed, I installed a new thermostat and then about 2 weeks later it started hammering in the valve area, I discovered a blown head gasket and water in the oil. I changed the gasket and the oil, etc.. adjusted the vavles and drove it back to work it started hammering again. I decided a couple of lifters must have collapsed. So I started replacing them all when I found about 3 or 4 were cupped and so I began removing the cam and sure enough about 4 lobes were gone. just a round circle left. I then cleaned everything inspected the bearings and installed a new CC .480 cam and in the process of trying to line up the timing chain I proceeded to turn the crank to find that it didn't want to turn all the way around. I backlashes and acts like their is compression in the cylinders that is holding it from turning so I installed the push rods and rocker arms thinking surely this would relieve the pressure it this was the problem but it seemed to a little but it still will not rotate but about 180 and then kicks back when trying to turn it with a socket. I can hear the compression bleeding off as I turn it but when I get so far it just stops like I am pushing against a sponge it gives a little but then goes back. Help!