Fellas, kind of confused here, I swapped a built 408 LS3 stroker into my 72 chevelle, I am getting close to finishing but am confused as far as installing the catch can. I have 1 nipple on each valve cover, I have a nipple on the passenger side of my NW 102mm throttle body, and another nipple on the front of the intake just behind the throttle body. I have a vented catch can with a filter on the top, however there is also a plug to make it a closed loop PCV system which I am told is the best route to go if the car is driven more on the street than the racetrack .How do I hook this up? Here is a drawing but I am not sure this is correct, some reading says that the nipple on the throttle body goes to the valve cover and provides positive pressure, while others say it pulls negative pressure? Any help on this would be appreciated,

 

that looks correct but im no expert...

when they put mine on they left the valve cover vented with a filter... im starting to think that wasnt correct bc there is no way for it to pull a vacuum...

 

What you have so far really doesn't serve the purpose of a PCV system. The catch can is a good idea, but it would be better to pick up fresh air before the TB, (but after the MAF if you have one), run it to the nipple on one of the valve covers for the fresh air side, then from the other valve cover to the catch can on which the filter has been removed
(and opening for it sealed off), then from the catch can to after the TB. This way there will be airflow thru the engine. Your diagram does not allow that.

 

Nothing correct about that at all. This is correct.






The PCV System needs to make a loop with no vac leaks in it anywhere to work right. I have one on my truck hooked up this exact way and works perfectly, been there for years.

Barb on the Throttle Body is clean metered air into the Engine, that is to the Passengers Valve cover.
Out of the PCV Valve in the Drivers Valve Cover to the Can.
Can to the port on the Intake.
Plug that Filter on top you want the system closed. No Vent.

 

Mine was done by Bobby Stipkovic and he routed it as shown by Merv.