Questions and Answers
CJ PCV System
Q. Vincent, I have a 1978 Jeep CJ with a 258 straight 6. There is an aftermarket intake manifold (Offenhauser) and 2 barrel carb on the engine. There is an aftermarket valve cover on the engine that has only one opening (besides the oil cap) the OEM had two or three I believe.
The problem I have is that when I connect the PCV valve it pulls air through the oil cap (push on oil cap). If I disconnect the PCV valve and insert a breather in the valve cover I get a lot of condensation in the breather filter. I think the PCV is the better way to go, so as not to let water build up in the engine. Do you agree? If so, what should I do about the air being sucked through the oil cap? Should I insert a breather where the oil cap is? (do they even make a breather that large?) or should I go back to an OEM valve cover?
Thanks for your time,
MatthewA. Not knowing how the intake is setup, it's hard for me to try and suggest a remedy. This much I can say, you are better off with the PCV valve that without it.
The theory behind PCV operation is this, A hose from the intake manifold goes to the PCV valve. The PCV valve usually sits in the top of the valve cover. Then another hose comes from the air filter housing, either from the inside of the air filter or through a breather filter, and to the crankcase. Now when the engine is running air is drawn from the air filter housing into the crankcase, through the PCV and into the intake. So there is a vacuum inside the crankcase. If you take the oil fill cap off, air will enter. This is normal. Some oil fill caps are the breather element such as on some older Chryslers.
The idea is to draw filtered air into the crankcase for obvious reasons, to keep the dirt out. It sounds to me like the setup you have does not allow this complete circuit of the PCV system.
One thing you can do is get a PCV valve grommet and drill a hole in the valve cover and insert the grommet. Then get a 90° elbow to fit and a short piece of hose to attach a breather element. This will complete the PCV circuit by providing filtered air the system needs to operate.
Additional Information provided courtesy of ALLDATA
