72455

The 455 in my 72 Cutlasd Supreme has aftermarket Milodon valve covers, and my current configuration is a pcv valve on the driver side with a hose that ties into the brake booster hose, and the brake booster hose is hooked up to the back of the carb. On the passenger side is an aftermarket oil breather cap with no vacuum hoses (or anything else) attached. (This setup is how it was when I bought the car)

I was talking to a friend of mine and he said my setup is wrong, that the oil breather cap is hurting my performance because without the right amount of crankase ventilation the engine is working harder to get the pistons back to bottom dead center because of the remaining pressure left in the combustion changers after the cycle.

The engine has had some work done by a previous owner, but as far what is unknown. I do know it has a Holley 670 Street Avenger, an Edelbrock 455 Oldsmobile intake along with headers and 3 inch dual exhaust.

My question is do I have the right setup with my pcv valve/vacuum system to maximize power and performance, and if not, what do I need to do? My friend
said to ditch the oil breather cap and use another pcv valve, tie it into the other one and run that to intake vacuum. He also said to run the brake booster vacuum by itself into the carb.

The car runs fine with no smoke on start up or while driving, and it doesn't "lean out" under the gun.

If anyone could chime in, I would love to hear thoughts and ideas, and if it is the stock configuration.

Thanks,
Dave

Fun71

Your friend is overthinking this. As long as there is vacuum to the brake booster and there is adequate flow from the valve cover breather to the PCV valve everything should be fine. The system needs to draw fresh air in from somewhere to allow air flow through the block to the PCV valve. With two PCV valves, there is vacuum drawing but where would the fresh air come into the system?

As for this your friend is way off base. The PCV system draws the blowby gases from the open areas in the block back into the carb to be burned, and there is absolutely no connection to the cylinders to do anything with the pressure in the cylinders.

72455

So what you to are saying is I don't need to change anything, correct?

joe_padavano

Is your "oil breather cap" actually a breather with vents or just a sealed oil fill cap? The side opposite the PCV needs to have some way for air to get in. The factory used a filter in the air cleaner and a tube from the valve cover breather to the air cleaner filter. This was done simply to comply with EPA requirements for a "closed" breather system. If your valve cover breather has vents and a filter, it's fine.

Something like this (as an example) is OK:

72455

Yup...that's what mine looks like...

shiftbyear

Always wondered why Olds change the configuration on the W30 cars (2 breathers OAI) . More blowby / fumes on the W cars? They must've had a reason.

wr1970

You are ok with your set up! The person who told you have your set up wrong needs to go fly a kite.

joe_padavano

I was going to suggest that the "friend" needs to read a book - a book on how PCV actually works!

72455

Sweet...thanks