Originally Posted by dreamstang
hmm ,never heard of that.to keep pressure from heat down?
Yes & No, it is to pull a vaccum on the crankcase, which is especially useful in SC & TC applications.
Helps eveything seal up better including your rings and keeps you from leaking oil all over.
With a SC/TC you can actually have positive pressure in the crankcase which is definitely not a desirable condition.
Ever seen a car push smoke/oil vapor out of a valve cover breather?
It is usually caused by bad ring seal from worn out or damaged rings.
Compression leaking past the bad piston rings and pressurizing the crankcase is most commonly the cause.