My friend has an extremly nice 1969 Cadillac Eldorado with a 500ci engine. The car has been sitting for the last 20 years I have known him. Over the last couple of days we have gotten the engine to run but it has a very bad miss. I found two cylinders that have no compression after the valve cover was removed we noticed the intake rocker arms don't move on the two cylinders with no compression ( large pushrod to rocker arm clearance). If you crank the engine over and hold the push rod down you can feel the lifter go up and down on the cam lobe. Any advice ?