Let's Talk Crank Case Evac
 

I am currently considering a vacuum pump because of the crank case pressure that builds up at high RPM in my 500+ rwhp NA LS2. I am going to be ditching the catch can that is pulling crank case vacuum from the valley.

I am looking to add a breather filter to both valve covers on the front end (currently have 1).

Should I add a larger line to the valley cover and put a breather on that as well?

Unless you are pulling a lot of vacuum, breathers smell and like to make a bit of a mess.

Are you looking for clean air in breathers or to relieve pressure? With a vacuum pump I'd pull from the valley and driver valve cover and left fresh air into the passenger valve cover.

I'd set it up like that even without the pump and have the intake pull it through a catch can.

never ran a vacuum pump by i have tried most other methods and IMO an exhaust evac is easily the best.

I just went through the same thing on my 408ci LQ4. You dont want all breathers on valve covers and valley cover because oil will get everywhere and will smell it with your windows down. You dont need a vacuum pump, plus they are super expensive.

Tried a bunch of different things but final set up is I removed my Rx catch can and installed a Mighty Mouse "black series" catch can or whatever the new ones are called. Three cans to choose from (race, draft, or PCV). The reason I suggest these cans are because at idle and cruising the vacuum from the manifold is enough to pull pressure out. But at full throttle if the crank case pressure is more than what the manifold can pull out then the pressure is then redirected through the breather on top of the can. Any other time the breather is closed kind of like a PCV valve. That way you're not getting oil vapors and smell under your hood 100% of the time. It will only be at full throttle.

I went with the "draft" can with -10AN oil cap fitting they sell, -10an dirty side fitting, -10AN line in between, then a 3/8" barb fitting for clean side, and 3/8" hose from clean side of can to intake manifold. Then put a breather on the drivers side valve cover. Capped the valley cover and port on passenger side valve cover. Works perfect and so much cheaper than a vacuum pump.

Or I agree with Tanus, exhaust evac is a good easy cheap solution also.

I reworked my evac system to pull from both valve covers. Looking at putting the Mighty Mouse can on this winter after I re-ring it.