Vented valve cover or no?
 

On my 64 with a 305E engine, this is the non california engine so there is no pcv but there is a crankcase fresh air filter on the driver's rear of the engine and the cylinder heads have the air valves that suck the emissions into the combustion chambers. My engine had a breather cap on the passenger side valve cover and I can smell blow by gases. I'm thinking this needs to be a closed system correct? I replaced the breather cap with a non vented oil fill cap on it and will see how it goes. Any comments will be appreciated because I have never seen this type of emission system.
Steve

Re: Vented valve cover or no?
 

Per our/your 6060GMCCLUB website. At top banner: Jolly's page/engine.....scroll down for explanation of crankcase venting. Answer is: no valve cover vent. Fresh air enters into the filter can, thru filter and etc. (on the filter can style motors)

Re: Vented valve cover or no?
 

and under each valve cover is a pcv valve screwed into an intake runner in the cylinder head.

Re: Vented valve cover or no?
 

Good info, is there a replacement number for these pcvs? Or can they be removed and cleaned with solvent?

Thanks,
Steve

Re: Vented valve cover or no?
 

Yes, they SHOULD be removed and cleaned with carb cleaner.

Re: Vented valve cover or no?
 

Thank you Ken, much appreciated.

Re: Vented valve cover or no?
 

Glad to help.

Re: Vented valve cover or no?
 

IF they don't clean up, the ac/delco p/n is cv623c. you may be able to pick up a pair of them on ebay.

Re: Vented valve cover or no?
 

On my '60 I too have a valve cover breather, but also have the filter tube behind the rdriver's side head. Do I need to remove the valve cover mushroom vented cap and put a closed cap too?

Re: Vented valve cover or no?
 

Don't think it makes any meaningful difference one way or another (to the motor). The Jolly page advertisement can be a guide or not. The can, in back, has it's own "intake". GMC called their system PCV. The advent of the vented valve cover was to release "crankcase pressures" said to cause oiling issues. So engineers decided to have it vent out thru there. They added baffling inside the "breather" to prevent oil from coming out. All kinds of set ups, pre smog/post smog.
Looks like stock for your motor is non vented covers.