4-RILLA

Wat up fella's, quick question

I was wondering why come in forced induction applications, we dont see a vac source connected to the PCV hardline? The intake manifold pulls vacuum on the crankase via this line and PCV valve when the intake has vaccum present, and I have seen where guys (myself included) connect a vaccum source to the valvecovers..I am using the exhaust evac kit from Mr. Gasket...but really dont "like" the oil flowing thru my XR1's....my engine does have excessive blo-by and is getting refreshed.

My friends Grand national uses a LT1 smog pump to pull vaccum on his valvecovers when his manifold see's 5lbd of boost..via a hobs switch and a racetronix kit for this purpose and it works flawless on his car for about a year and a half now..he DID modify the pump but it wasnt nohing major,,just got a write-up off of the Turbo Buick forums,

What I was wanting to do,,is Tee into the hardine right at the midway point from the PCV valve to the intake vac port with a electric vac pump...I would put a ONE WAY check valve inline right under the throttle body to ensure that when the vac pump kicks on..it will not pull air OUT of the intake..the flow of the system would only flow from PCV to intake vac port and then under boost the check valve would unsure that the Vac port would not release any boost pressure BACK toward the PCV valve..but what WOULD happen is the crackcase flow would go PCV valve to electric vav pump..thru a inline oil separater...

It seems like this would have a more dirct pull on the crankcase rather than pulling vac on the valvecovers as the Turbo buick guys do, and the electric vac pump would be "transparent" to the intake vac port due to the one way check valve being inline and the pump would only kick on when the intake is pressurized anyway, so the pressurized flow would STOP at the check valve...but ont he OTHER side (PCV SIDE) of the check valve pump would be pulling excess crank pressure.

Thought Suggestions?

Thanks
Rod

MikeGyver

They both dump into the same area, lifter valley.

The PCV valve hole in the intake manifold goes though a sheet metal baffle with 4 small holes in it. It's more of a restriction than the valve cover hole, you'd be better off just goin there.

4-RILLA

Yeh I looked at the LT1 intake really good when I was pondering on this...I didnt think that the port on the intake would be a more restrictive path to crackcase...guess the why GM has the vac port pull vaccum there instead of valvecovers...may have too much crankcase oil vapor entering intake I guess huh?

The thought of running a breather on the pass side valvecover to vnt the crackcase pressure until vac pump kicks on has crossed my mind..because if I have the pump kickon at 5psi boost then I have a situation where the intake isnt pulling vaccum on the crackcase because it has 5psi of boost in it and if there is no vents/breathers on valvecovers...the crankcase pressure has nowhere to go until the vac pump comes on at 5psi...but dam, with a breather there..the vac pump would be pulling atmoshpere from THAT valvecover when it does kick on?

Walter

I only use this system on both my Procharged cars

4-RILLA

Pretty nifty, are both of your procharged cars LTx cars? how do you have those plumed into the crankcase trace, are you juss running a hose from each valvecover to each catch can? did you block the stock PCV system in the intake?

I am Looking into something like what you are doing, but at the same time I see then Turbo Buick guys running the Modified LT1 smog pump evac system with GOOD results, I think most of them have a hobbs switch in the intake that kicks on the pump at 3-4 psi of boost pressure..Only thing I really wonder with that is where does the excess crankcase pressure go until u hit 3-4 psi and the pump turns on...I would imagine with the PCV system intact you would have the PCV valve pulling out excess crankcase pressure while vacuum is in the intake...but then again maybe until the pump kicks on..the crankcase would vent throught the line going to the pump until it kicks on...

Thanks for those pics...would like to see how those are orientated under the hood of your car.

Walter

My FI LT1 camaro i have a 3/8's hose/fuel line running from each valve cover to the Vented breather catch can, my breather can has 2 barbs for both valve covers. This vents and purges any crankcase pressure,

I have the non vented closed loop can running inbetween the vally port and the PCV valve port with a GN check valve in place to insure no boost enters the crankcase.

I have the throttle body port cap off

4-RILLA

How has this set-up worked for you? Have you had any rear main seal leaks under boost? or oil pan leaks?

Thx

97WS6Pilot

4-rilla,

I really like the idea of the smog pump on a hobbs switch. Sounds like it would work great. The catch can really only needs to go to one valve cover. If you have more blowby than that then you really have problems.

Walter

True, but i like to vent both valve covers , even it out , nothing to to with to much blowby.