Valve cover breathers / crankcase ventilation, Essential???

[The T-man]

Valve cover breathers
crankcase ventilation

Is it required to have breather/crankcase venting?
I have a gen 1 small chevy I am building, and I hate to cut into the custom valve covers I have
could you just do a small vent in the back of the block valley, say 4 an to a remote resevoir, is that enough, or a bad idea?
I see some track motors with a vacuum pump, what's the deal with that?

Will it cause serious problems to NOT have venting?<<<<<<<
any good pics of what you've done please link
thanks!

[Vegas69]

You must have it and 4 an is not enough. Blown seals and excess crankase pressure and moisture. Excess crancase pressure causes loss of power and possible oil pressure issues.

[chicane]

Originally Posted by The T-man

Is it required to have breather/crankcase venting?

I have a gen 1 small chevy I am building, and I hate to cut into the custom valve covers I have could you just do a small vent in the back of the block valley, say 4 an to a remote resevoir, is that enough, or a bad idea?
I see some track motors with a vacuum pump, what's the deal with that?

Will it cause serious problems to NOT have venting?<<<<<<<
any good pics of what you've done please link
thanks!

Here is a link to a similar discussion that pretty much stemed from the issues that Rupp had with Bad Penny at the Optima/HotRod Ultimate Street Car event, post SEMA. It touches on this subject matter and addresses most of your inquiry. Albiet this thread is more geared toward the LS series engines... the principals are the same.

The long and the short of it... yes, ventialtion is important. How you go about it can be done several ways... but without going to a pan evacuation system, you will need to plumb that manifold and/or the valve covers as well. But... it really depends on the engine. Some have more blow-by the rings and/or windage problems than others.

It may be in your best interest to give up on the idea that you are NOT going to cut into the valve covers now. If your crank case pressure is bad enough... you will have no choice... but to cut.

A -4 AN is not going to be nearly big enough. The minimum... would be either a -10 or -12 AN.

Vacuum pumps pull the crank case pressure and it improves a few things. It helps seat the rings better... it helps with oil drain back to the oil pan... and it helps with engine sealing.

Will serious problems rear their ugly head if you dont control ventilation ?? Yes... you could have a number of problems. Leaks, oil starvation issues, blown seals, combustion issues, induction tuning issues and overall poor engine performance will be right in there.


Here are a few pictures of my last gen 1 SBC build. This was during the mock up stages... but it shows the breather tubes in the valve covers.

Link one

Link two

[Steve Chryssos]

It's one of the toughest issues facing pro-touring enthusiasts since we jam on the brakes AND mash the throttle. Minor fabrication is usually in order. I like to see a well baffled system and if possible a PCV system--Especially on a Gen 1 small block or big block where valve seal design is only so-so (lots of arguments on PCV).

Oh, and if you do a remote tank DON'T mount it on the firewall. Very stinky. Mount it as far forward as possible.