PCV Valve

[tri-power 250]

I was checking the timing today and noticed the PCV tube collapsed. I bought a new PCV valve and changed the rubber line. Why does this little, probably over looked part, cause an engine to idle poorly? I changed it out to a new one, and now the car runs great.
Thanks,
Ken

 

[ludwig]

It vents pressure out of the crankcase when the pistons draw back down on the intake stroke. So if there is more pressure below, you get an energy sap. That and other stuff that more well informed guys can tell you about.

It is a great improvement on the straight breather tubes from the early sixties. The Falcons especially smoked out the breather under the engine, even if they didn't smoke out the tailpipe.