wstefan20
New member
As an update, I'll be finalizing the hookup today, but while I was at the junkyard I took a look at a few supercharged 3800s. What I found was interesting. On the n/a 3800s (L26/L36) the crankcase vapors travel from both heads via the lifter valley to the front head where the gasses are routed to the pcv valve and expelled through the intake, while fresh air is drawn through the upper intake manifold either via the throttle body or vertical pipe.
On the supercharged 3800s (L67/L32), the pcv is exactly opposite! The crankcase vapors travel through the lifter valley between the heads and the rear head expels the gasses up to the pcv valve while the front head is the breather that passes up to either the throttle body or vertical pipe!
What this means:
A few things. First, if you are going to re-route the intake to a breather, while on the supercharged engines you'll want to place a breather on the oil fill cap (front head), if you're going to block off the intake on any n/a 3800s (such as spacer with no provision for pcv, L26 and cap upper pipe, etc.) to achieve actual pcv function, you need a breather on the REAR valve cover!
Placing one on the front of n/a cars actually completely bypasses the pcv!
Also, drilling a hole through the vertical pipe as described in many famous L26 intake swaps is also negating the pcv system entirely as you are hooking your pcv intake to VACUUM! When you hook the intake to vacuum, you've now equalized the pressure between the manifold and the crankcase. Same thing as running lines from both valve covers directly to the manifold with no pcv valve!
So for all those who have used this method, I would strongly advise for you to plug the hole you drilled and either route the intake to a breather, or to an inlet before the throttle body (remember anything after tb is vacuum).
If this method works, both n/a, supercharged, and turbo cars alike can run catch cans and fully functioning pcv systems without having to run extra lines or breathers to accomplish the same thing!
On the supercharged 3800s (L67/L32), the pcv is exactly opposite! The crankcase vapors travel through the lifter valley between the heads and the rear head expels the gasses up to the pcv valve while the front head is the breather that passes up to either the throttle body or vertical pipe!
What this means:
A few things. First, if you are going to re-route the intake to a breather, while on the supercharged engines you'll want to place a breather on the oil fill cap (front head), if you're going to block off the intake on any n/a 3800s (such as spacer with no provision for pcv, L26 and cap upper pipe, etc.) to achieve actual pcv function, you need a breather on the REAR valve cover!
Placing one on the front of n/a cars actually completely bypasses the pcv!
Also, drilling a hole through the vertical pipe as described in many famous L26 intake swaps is also negating the pcv system entirely as you are hooking your pcv intake to VACUUM! When you hook the intake to vacuum, you've now equalized the pressure between the manifold and the crankcase. Same thing as running lines from both valve covers directly to the manifold with no pcv valve!
So for all those who have used this method, I would strongly advise for you to plug the hole you drilled and either route the intake to a breather, or to an inlet before the throttle body (remember anything after tb is vacuum).
If this method works, both n/a, supercharged, and turbo cars alike can run catch cans and fully functioning pcv systems without having to run extra lines or breathers to accomplish the same thing!
