Engine breathing

[J-440]

When it comes to letting your engine breathe via pvc valve, oil breather tubes, etc. what is the standard I.D. of the hoses coming out of each valve cover? I have a supercharged 440 which will be running soon and was just curious. I have -8 lines coming from both valve covers going into a breather tank. This ok?

[Vegas69]

I'd recommend -12 or equivalent.

[J-440]

-12 huh? I can see if you were running a vacuum pump to seal the rings better, but for my application? Is there a formula for figuring this out based on cubic inches vs the amount of air that needs to be bled? Thanks Vegas.:thumbsup:

[camcojb]

I don't know of a formula but I think #8 is too small for breather hoses. I used #12 on mine.

[Vegas69]

A supercharged application with that may cubes calls for at least 2 -12's in my opinion. That is, unless you just plan on putting around to car shows. :unibrow: Excessive crankcase pressure has no positive side effects. You lose power and seals leak. Remember, this is positive pressure not negative with a vacuum pump.

[GregWeld]

Just to be sure.... you said you're running a PCV valve? I would ASSume then that it's got vacuum to it? OR are you just running -8 VENTS to a breather can?

My brother in laws blown - dual carb - 383 - uses a "normal" PCV to the base of one carb for vacuum - and of course - a vented breather in the opposite valve cover.... and this works fine for a street driven blower motor. If he was hammering it on the strip - then I'd go with Todd on the -12 vented lines to a breather catch can.

[J-440]

No PVC valve just the breather tubes and catch tank. Guess I'll order up some -12's. Thanks guys.