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[garickman]

O.K, I am trying to get all my ducks in a row on the engine build of my 1967 Pro-Touring Police Tribute Car. I am at a point where I need to think about positive crankcase ventilation and I will design my firewall to house certain components. I have a few questions I hope someone can help me with?

1. Does ventilation have to come from the valve covers or since I am having a custom intake manifold made can some type of breather be incorporated into the manifold?

2. What is the difference between an oil breather catch can and air/oil sepertor?

3. If ventilation does have to come from the valve covers, do both covers need to be ventilated?

My plan was to use a -12AN fitting on each valve cover and run a -12 hose from each valve cover to a -12 Tee adapter and run a single -12 hose to a catch can breather mounted on the firewall. Since my valve covers are being machined from billet I would like to keep them smooth and clean and would like the ventilation to come from the back of the manifold with a single -12 line running to a breather catch can if that is possible.

Is any of this possible?

[ArtosDracon]

It's possible, sure. If you can find a happy place to put it that won't interfere with the distributor or throttle linkage or fuel lines then go for it. The issue is generally with convenience. The crankcase ventilation would theoretically be better at the base of the intake because of the rather large oil drainback passages.

[parsonsj]

Greg,

A functioning PCV has two ports: a filtered fresh air inlet, and an outlet that goes to the intake manifold. The whole idea of a PCV is to use manifold vacuum to pull clean air into the motor and draw out dirty air and burn it. PCV systems greatly extend the life of a motor... they aren't just for "smog" or for preventing oil leaks.

In order for the manifold vacuum to not just pull the new clean air right back before it circulates, the inlet and outlet of the PCV system need to be as far away as possible from each other. That's why most OEM's put them on opposite valve covers and usually opposite ends of the motor as well.

My point is that if you want a working PCV system, the *best* way to do it is via the valve covers.

jp

[ArtosDracon]

Great point John, a PCV system is VERY different than just a crankcase ventilation system, which one you need would depend a lot on the application of the engine.