Ok. I am having a crankcase pressure issue. I have a brand new built forged 383 and I have a supercharger pushing about 12-14lbs of boost. I have a little issue with dipstick popping out. I don't think my rings have had time to seat, and with that much boost, it is causing alot of crankcase pressure and blow by. My datalog shows that under load, my map reading is about 104. Around idle and low rpm, its about 50. I have 2 holes on each valve cover. My driv. side valve cover is capped off, my pass side rear valve cover hole has a check valve, and a hose running into the intake after the maf/before supercharger inlet, creating a vacuum. On the front pass. side valve cover hole, I have a breather. My question is, if I took out the breather and run a check valve out of that hole, with a hose running into a catch can, then to the brake booster hose, will this work and create more vacuum so that the map wont be so high?

 

Do you have anything other than the stock 1 bar MAP sensor? Appears not, since you are seeing 104kPa at boost, and that's about the upper limit of the 1 bar sensor. With 12-14# boost, at max boost you should be seeing closer to 2 bar/200kPa. Even under moderate loads I would expect a positive MAP.

With the intake under atmospheric pressure, or even boost at part load, there is no "vacuum". And you have no "positive" crankcase ventilation. Tieing into the brake booster vacuum hose isn't going to provide any more vacuum than the stock PCV location/hookup. How is your PCV valve routed now?

I thought the norm with a blower motor was to route the PCV valve to the suction side of the blower ducting, and to put an oill separator in the line from the PCV to the ducting. That way the PCV valve is at a lower pressure than the manifold under boost, and will pull vapor from the crankcase.

This really is unique to a blower setup, and I would think that on the Forced Induction forum you would find dozens of people who have already solved the problem. Of course it its a problem related to excessive blowby, and not temporary ring seating issues, you may have to start all over again at the pistons, rings and cylinder finish.

 

The hose running from my pcv valve is t'd into the suction side of the blower after the maf along with the hose from my pass. side valve cover.

 

If you have both the line from the valve cover and the line from the PCV valve connected to the same point, there is no "cross flow", which is the intent of the stock system, but it should relive the pressure in the crankcase.

You also say you have a check valve in the line from the valve cover to the blower intake duct. Which way is that valve facing? Which direction of flow does it prevent.

 

Cross flow? The check valve is preventing air from going into the valve cover. Basically pulling air out. What should I do with the 2 lines if they shouldn't be in the same place? I thought as long as they are both used for vacuum, they can go to one vacuum source.