Street/Strip Crankcase Vacuum using a PCV Valve

bjkadron said
Sorry to drag up a really old thread. This is a very creative solution. I have been considering doing something like this but with a vacuum/ catch can and pluming it to both the pvc/intake manifold and the exhaust-powered E-vacs so in theory when manifold vac goes down, the evacs kick in. Just need to figure out a crossover for the two vacuum sources but it seems like it would work well. How did you do the crossover from your vacuum pump? or did you just run it as the only option?

I put a check valve on the exhaust of the electric pump. If a situation arose where the pcv could not keep up, the idea was that the check valve would open to relieve any pressure buildup. That single check valve was the same valve as used on the exhaust powered evac systems.

In my application the pcv valve draws way more vacuum than the electric pump during casual driving, which allowed me to activate the electric pump only when I was going to make a WOT pass. I was turning the pump on manually at the time, although I could have turned it on automatically with my WOT switch. Lucky for me I eventually forgot to turn the electric pump on, to my surprise data logger told me the pcv valve was enough and I didn't actually need the electric pump. From that point I eliminated the electric pump and moved the check valve to inside the breathers. To this day when I remove a breather to add oil to the engine, the top half of the check balls as well as the inside of the breathers are clean and dry.

I should add that it's important to keep the engine sealed, that way the pcv only has to deal with actual blow-by rather than external air leaks. In my case the pcv valve draws 15"-18"Hg in the crankcase during casual driving, making it hard to maintain a seal over time at the top of the china wall. Initially I made spacers to fill most of the gap (raised port heads), but still eventually Ultra Black would get pulled thru. I almost started using Right Stuff instead, but didn't want to have to pry the intake off when the time came. Now I back up the Ultra Black with a thin band of Right stuff applied over the outside after installing the intake, fixed the problem.

Grant