NHGuy

Chevy 383, I have some aluminum finned valve covers. And it looks bad when they aren't clean.

I bought some new grommets for my breathers, they come from the factory without a hole and I'm wondering how much to open them. I don't have a problem other than oil getting out onto my valve covers because the old grommets have gotten hard and have shrunk away on their outsides.

Guy I know is an old drag racer and hot rodder, He says some folks just cut some slits in them, I think that would not work here since my breathers are just leading to the outside of my flame arrestor. Not like a PCV. I have no baffles but my breathers do have some media in them to slow down the oil.
I'm thinking a small opening, enough to allow a little crankcase air through.

Whatta ya think? big opening, medium?

Wally

iTrader: (1)

Ive always cut a half moon shape on the bottom of ones ive had in the past and pointed the opening to the exhaust side of the valve covers....i dont know if thats proper or not, just worked for me. Ive seen all kinds....fully cut open...or just small 1/4" hole punched through...cant say whats the best.

SB

iTrader: (1)

A restriction to your crankcase psi is bad. That can cause seals to leak.
To be safe You want the openings as large as your vc fittings opening. If you suck oil you need vc baffles and/or fitting location moved.

NHGuy

Cool, large opening then.