PCV Purpose

Q: PCV Purpose

Is the PCV valve required for crankcase ventilation if I have a breather in my valve cover?

A: The purpose of the PCV is to ventilate the crankcase of by-pass gases and while helping to prevent any positive pressure buildup which will blow oil past seals and out your dip-stick tube. These gases contribute to oil breakdown and internal varnishing. Using your intake vacuum as a source, the gases are “pulled” from the crankcase. Just having a vented breather is not enough to properly ventilate the crankcase.

Q: Ok so I have to have the PCV valve (I was hoping you would say I didn’t!) Does it have to be located in the valley pan or can it be in the valve cover? I bought a replacement valley pan made out of rolled aluminum and it doesn’t have a hole for the pcv valve. Also. isnt the PCV valve a piece of smog equipment? What did early cars say from the 50’s have for crankcase ventilation?

A: Installing one in the valve cover will work fine. Before PCV valves, most motors had an open vent tube coming from the lifter galley. Typical on early SBC was a vent pipe the attached behind the distributor to the block. The other end had a “baffle” at the back of the lifter galley. On a weak motor, you could see the blue smoke coming out of the vent tube under the car. Imagine the smell! And by the way… another reason the have a PCV valve is to help reduce engine blow-by odors and fumes inside the car.

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