Questions and Answers

Chevy Monte Carlo Engine Breathing Q. Vincent, I have a 1987 Chevy Monte Carlo SS that has a bad oil leak. The engine is a brand new 383 cid, 350 block with a 400 crank, stroker motor. I think the front seal is the culprit and that it may have been caused by allowing to much vacuum on the crankcase. Therefore, I would like to know if I can use two PCV valves on the motor to keep it a closed system.

It currently has one PCV valve coming out of the valve covers. The other valve cover has a place to put another PCV valve but I currently have an open ¾" elbow connected directly to the breather. This was not my design and the mechanic thought that would allow the crankcase to have clean air supply.

I believe the lack of another PCV valve created to much vacuum in the crankcase. At Idle the engine creates about 18" of vacuum, and since it is new, the rings have not seated yet. Is it possible for this amount of vacuum to cause a front seal to leak?

Does the crankcase need a clean air supply? Would two PCV valves allow enough air flow to adequately vent the crankcase on this new engine which the rings have not seated, without creating too much vacuum? Should both PCV valves be connected directly to the intake manifold or the air filter?

I can not leave it the way it is and my only other option is to buy a separate crankcase oil filter and convert it to an open system. I would like to know your thought on the subject.

Thank you,
Tim

A. Too much vacuum in the crankcase would cause it to suck air in the front seal. Too much pressure building up would cause it to blow out the seals. With it running and all the PCV stuff hooked up as designed, remove the oil fill cap and see if it blows out or sucks in. You can even measure this with a gauge. There should be a slight amount of vacuum there.

There needs to be a fresh air supply in one valve cover so excess vacuum or pressure does not build up. Maybe the seal is just bad or the balancer has a nick in it? Most times on a stock engine with PCV problems they clog and allow pressure to build in the crankcase which makes oil blow out the rear main and front seals as well as the valve covers.