Do I NEED a PCV VALVE or...?

[CharlieJ]

My question is do I need a PCV Valve or can I just run a positive crank case line with no valve? I don't see much of a purpose for the valve other than being another part that needs replacing.

 

[Diesel1]

Whats the pcv on? well on my corvette it helps to keep oil from the carb, but high rpm seems to defeat all. Thats why newer cars have an actual filter with one way valve.

 

[CharlieJ]

This would be for my Rx7.

 

[ARCOgraphite]

Yes you need it. What's the actual complaint? Maybe you should throw those extra spark plugs away too! An dth e bumper jack. The pcv also act as a backfire preventer, unless you want to blow the oil pan off your car.

 

[eljefino]

The valve cuts flow at idle; if you had one you should probably keep it.

 

[CharlieJ]

Looks like I'll be adding a PCV valve to the "things to do" list.

 

[mechtech2]

Keep the proper valve in there, for sure.
It meters flow at different throttle [ thus manifold vacum] settings and conditions.
It also is an anti backfire and flow device.

 

[CharlieJ]

I need to go buy one because it does not have one right now.

 

[wiswind]

If it originally had one, you need it.
A PCV valve is more than just a one way valve.
There is a spring inside that holds the plunger (part that you hear rattling when you shake it) off of a valve seat.
The plunger is tapered.
Under low vaccum, the PCV valve is fully open.
Under high vaccum, the PCV valve is pressing against the spring.....restricting the flow through between the tapered end of the plunger and the valve seat.

Why is the flow reduced under higher vaccum?
The intake manifold vaccum is low under high RPM.....and it is high at idle.
Higher vaccum means MORE airflow through the same sized opening as compared to at low vaccum.
You don't want maximum flow through the PCV valve at idle.....when the motor is running at it's lowest RPMs.

 

[CharlieJ]

Looking at the Factory Service Manual (FSM) there is a "check valve" between a port on the block that runs to the intake manifold. I'm assuming that this is the PCV? The only reason that it does not have one now is because the instructions that came with my Racing Beat™ intake manifold told me to remove it. I did not know any better at the time.