Quote Originally Posted by Blknight.aus View Post
Im pretty sure that Im going to plumb it in so that the drain back is above the oil level which means that its mandatory to fit the one way valve. On that note and this is the only thing that I am in disagreeance with the guys who made the thing in how they want it fitted up. The manual specifies that if your fitting the return lower than the nominal minimum oil level that you dont need the check valve. Thats fine under normal operating circumstances but if you slope it hard enough (bet some of you will) blow out a set of rings crack a piston, have a turbo start to vent boost pressure into the crank case OR for osme reason the piping/flow path for the crank case gasses becomes blocked then the sump will overpressurise push the oil up into the provent and then into your air intake.
Hmmm. Yes that's pretty much what happened. Except it didn't need a slope, just oil trapped in the outlet valve area which could only exit via the hose to the intake.

Post 114 onwards shows the top side damage to a 4BD1T: http://www.aulro.com/afvb/isuzu-land...lassic-12.html
I reversed the flow of the provent to stop it ever happening again. Now the oily air comes in the bottom and clean air leaves the top. Gravity is helping the seperation, not fighting it and trying to send oil back to the intake.
Due to the suspected broken rings I still have a lot of blowby but with the Brovent (tm) modifications this is causing no problems and all return air is clean of oil.