Understanding Plenum design

[chasracer]

I currently have the plenum top off to do a spacer upgrade and I cannot understand the reasoning for the oil cavity in the center of the bottom manifold. It does however explain some of the lost oil between oil changes as it is rather obvious that some has made its way into the intake tract.

Can anyone explain the engineering idea behind this to me. If the oil area was really well sealed (and I see evidence that it is not) then okay - I guess. But even then I cannot come up with a reason for doing this.

Help!

[tollboothwilley]

Oil in the intake air will lower octane. This is the reason that many people have installed OIL CATCH CANS. Between the Lower plenum and the passenger side(bank 1) valve cover you will notice a hose. It connects to the PCV valve. Installing a filtering device(catch can) in the middle of this vacuum line will help to keep oil out of your intake.

It all has to do with emissions. You can't just ventilate gases into the atmosphere. They have to control where those gases go.

[Poyzinous]

yeah... its crankcase ventillation. It also helps keep positive pressure within the engine. its also necessary for mother nature. lower emissions