Before I started this I put a vacuum gauge on my dipstick tube to check to see how bad my blow-by was if I had any at all. The needle fluttered back and forth at idle but under boost it steadied out but didn’t show pressure. And before anybody suggests a valve job the needle doesn’t fluter when hooked up to the intake. I’m guessing the PCV valve opening and closing or the turbulence of the crank and pistons moving is what’s causing it.
I installed a G.M. electric smog pump to use as a crankcase evacuation pump. I had to do a modification to my PCV system. I had to build a check valve so my PCV system would pull the crankcase into a vacuum. The way I have my oil catch can set up is basically an extension of my valve cover. I have the PCV pulling vapor out of the valve cover via the catch can. During boost any blow-by would then got to the airbox. In order to pull a vacuum in the crankcase I had to put a check valve between the oil catch can and the airbox. The check valve had to be big enough to flow blow-by into the airbox without creating back pressure in the crankcase. With the airbox vent hose being 5/8” I made the check valve with 5/8” barb fittings. I hooked the evac pump to pull a vacuum on the catch can.
You need to do some modifications to the electric smog pump before you use it. Go here for the mods:
http://www.turbobuick.com/forums/gen...-pump-how.html
I don’t want my evac pump running all the time and when the intake has vacuum there is no need for it to run. So I have the pump hooked up to a relay and a Hobbs switch. The switch is set for 2 p.s.i.
Now at idle my crankcase is at 6-10” HG. Under boost the evac pump pulls about 3” HG.
A.J.