What causes pressure in the crank case?

[GWTW-000]

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?

 

[Anonymous]

The very first thing I would do is a leakdown test. This will pinpoint where the problem is. Sometimes an exhaust popping can be nothing more than a weak plug, but could also be a bad exhaust valve seal. Crankcase pressure is only one thing...Blow-by. Plain and simple. The rings aren't sealing well. Adding compression to the engine makes the matter worse. After your leakdown test, and solving the popping problem, I would give the engine some break in time to see if the rings seal up. Of course the leakdown test will also let you know if it is all 8 holes leaking or maybe one bad cylinder (Something such as a cracked ring etc) If that's the case, you would have to dig in to fix the problem. I think you're going about it the right way..Don't just band-aid it if there's a real problem. But in either case, a crankcase evac is pretty much a nescessity on any high load application and excellent advice. Let me know what you dig up.

Felber

 

[marshmaster pat]

Yep, seen crankcase pressure on a motor that was bad enough to push the oil dipstick loose. New rings on that head got rid of that problem, but there were many more. The motor was junk and had suffered much abuse.

Can polish and paint a turd, but it is still what it originally was.