Valve Cover Breathers
 

I have a theoretical case scenario I was wondering if I can get some comment on by the engine experts. If you have no valve cover breathers on either valve cover (V8 Engine of course), and are using just a PCV valve, can the crankcase pressure build high enough to cause the rear main seal to fail?

Re: Valve Cover Breathers
 

YES! A PCV system requires a breather to be a ventilation system. little or no vacum under full throttle which is when the engine is making the high amount of back pressure.

Re: Valve Cover Breathers
 

I found out by accident that you need a breather installed if you use a PCV valve system. I didn't lose a rear-main seal but I sucked a valve-cover gasket up pretty good! :D