Bad30th

iTrader: (13)

I'm wondering why the LS1 has the extra hose from the pass side valve cover to the TB, when there's already a vent via the PCV into the intake from the pass side valve cover. Seems like one would be enough to vent the crank case, only one line from the driver side via PCV...

Why two ?

The reason I ask is this :

I have a check valve in my PCV line to keep from boosting the crank case via the PCV. I'm not seeing nearly the accumulation of "goop" in the catch can lately, I'm thinking it's because I have a check-valve in the PCV line to keep from pressurizing the crank case, and the flow is taking the path of least resistance out the line that goes to my blower inlet for vacuum (stock it goes to the TB). The check valve takes .3psi to open (it's the common McMaster/Carr one).

Can I just cap off the line that runs from the pass side valve cover to the intake and evac the crank case via the PCV ? I just don't want to be sucking all the catch-can goop into my blower via that redundant line...

Any thoughts ?

Thanks,
Rob (Bad30th)

Bad30th

iTrader: (13)

No, that's the driver's side. That line goes intake->evap.

The pass side has two valve cover exits - one for the PCV system and one that runs to the TB. Why is the TB one required ?

Bad30th

WS6FirebirdTA00

iTrader: (33)

i had the same question a while back for different reasons, i got mixed responses. i ended up leaving it on there. i would assume its to draw more air out with higher tps

Bad30th

iTrader: (13)

TTT, anyone know why it's there ?

It seems like a higher TPS would result in lower vacuum (higher MAP) so the crank evac flow would be diminished if anything...

Bad30th

Mike94ZLT1

iTrader: (3)

I relocated the one with the stupid green valve. I know have Corvette FRC's (fuel rail covers, not my fixed roof coupe) with the one hole on the drivers side, and it looks 1,000,000x better.

Bad30th

iTrader: (13)

PASS side guys. Not driver side. Not fuel lines or evap, not PCV.

I'm asking about the line that runs from the front pass side valve cover to the TB.

Why is it there if the PCV provides crank case evac ?

Bad30th

WS6FirebirdTA00

iTrader: (33)

its the suction effect from the airflow, the vacuum might not be high but the airflow and air demand it, which in the end causes a vacuum on the pcv tubes

Bad30th

iTrader: (13)

Ah, gotcha. I think that makes sense.

If the vacuum is low (higher MAP) the intake suction via that second line takes the place of the PCV idle vacuum to evac the crank case ? This way we get evac at all throttle ranges ?

Thanks !

Guess I won't disconnect it... I sure hate the idea of the PCV catch can being bypassed and all that crap going into my blower though...

Maybe I need a second catch can haha.

Bad30th

2xLS1

iTrader: (25)

That is the fresh air intake for the crankcase. As the PCV system evacuates gasses from the crankcase through the ports on the back of the valve covers, they are replaced by fresh air through the hose going to the throttle body.

Bad30th

iTrader: (13)

Thanks ! This makes sense now - the air coming out of the PCV lines has to come into the crank case from somewhere (hopefully not past your rings, right).

So, the second line is what allows the pcv system to bring air into the crankcase to facilitate PCV flow.

Maybe I'll stick one of those clear fuel filters in the line to see if any catch-can/crankcase funk is coming through it the other direction.

Cheers,
Bad30th

jimmyblue

iTrader: (11)

You want the PCV makeup air not to bypass the MAF,
so it's drawn from the last handy spot - out of the TB
casting, before the blade.

But, at WOT this spot is under some vacuum against
the filter and MAF pressure drop, and it's not check-
metered, so this is where you can draw up a fair bit
of oil fog if you have any significant blowby pressurizing
the case.

I put an oil trap in mine. But the motor is still tight
enough that I haven't caught any to speak of. That,
or I don't spend enough time at WOT

WS6FirebirdTA00

iTrader: (33)

ok cool, it just doesnt seem like it would be too effective though in certain ranges