Thread: Help with PCV for turbo setup

Originally Posted by 94GrandPrixSE

I read your write up a few times ton of info great post thank you! I mostly understand what I have to do but I don't understand the point of an catch can on the intake side. I apologize for my lack of understanding here haven't had much experience with pcv systems because I haven't need to yet. Also I do not understand if I could just run hoses off my valve covers instead of going through the UIM. I could make a cleaner looking setup if It would work and should eliminate designated sides to use for intake and dirty side?

You are correct. If you run your own setup external you wouldn't have to worry about the heads, but you would need to tap both heads. The air intake catch can is to catch any stray oil or moisture from the turbo or if the system reverses. Basically, during high boost, the regular vacuum side of the loop completely closes off (check valve) to prevent the crankcase pressurizing, but the engine is still producing positive crankcase pressure. So the pressure causes the loop to "reverse" and the intake becomes like the vacuum side and vents crankcase pressure to before the turbo, so without the catch can there, all the vapor and oil mixture will spray onto your turbo. Again, this only happens during high boost so it isn't much, but personally, I wouldn't want to spray that into my turbo.... it's up to you.

If you route everything external (which is actually what I'm planning on doing), you need to install baffles to make sure the oil doesn't get sucked up or clog the lines with buildup and you'd have to do BOTH. Then you'd have to drill and tap where the old pcv valve went and run one external. The tricky part is that the pcv valve is actually designed for the flow rate of our engine, so the only universal one that will work would be this one: Dual Flow Adjustable PCV Valve – M/E Wagner Performance Products. Your other option is to somehow create an inline "holder", or find a way to adapt a grommet like off a sbc. Most of the sbc used a similar pcv valve that just uses a grommet in the valve cover to hold the pcv valve. The latter option would be the most practical.

With both options though, you will either have to find a place on the valve cover that has enough clearance for the lifters both for the pcv valve and the baffle, or you'll have to have custom valve covers made, or you'll have to pick up another valve cover with oil filter hole and find a way to add baffling under it and install the grommet for your pcv valve and hose.

Obviously you'll have to remove both valve covers, drill the holes for the pcv, install the pcv valve in one of the valve covers as mentioned, then route the pcv one to a catch can, then to a source of vacuum, and the other one either directly before the turbo, or to another catch can then to before the turbo.

Oh, and do NOT forget the one way check valve after the pcv valve side catch can going to the vacuum. The pcv valve does a good job at stopping backfires, but not so good at completely closing with boost, so without it, boost will leak past and pressurize the crankcase and cause issues.