I recently rebuilt a 440 out of a 76 New Yorker for a project I'm working on. This weekend was time for a first start. When cranking it showed no compression in any cylinder. Pulled the rocker assembly and it has compression (about 75psi but no air in I didn't expect it to be real high). Put the rocker back on lose and no compression. All new parts, pistons, cam, bearings, heads rebuilt (surfaced but not more than a few thousandths removed). Parts came from the engine guy that did the machine work. Cam should be like a 70 magnum grind, pistons were 30 overbore with a bump to 9.5 to 1. I did the assembly on the block, no problems during bolt together. Any ideas what might be the problem? Possible wrong cam? Pulled another 440 valve train and checked the lifters for difference (Where the push rod sits it is same height but overall length 1/6" taller) , push rod length, all the same. Checked it for another type new lifter but they were the same.