What causes pressure in the crank case of a car (Caddy) motor? We have just built a new long block 500 Caddy motor. It's the high compression model. We have installed a new cam, rocker arms, lifters and springs from Cad Company. When we started it, the left side is poping in the exhaust. The mech. said it sounds like a valve is sticking a little and should seat in a little bit. We still have it in the shop and have ran it only about 30 min. so far. I have ordered a Mr. Gasket evacuation kit from Jeg's to solve the problem like Waterthunder sugested on another thread some time ago. What causes the pressure and am I only treating the symptoms?