Using a PCV Valve from valley pan in rear of motor to back of intake manifold on a Offenhauser  3/2 Aluminum manifold. Do you use a breather cap on the oil fill into the valley pan or do you use a non-vented oil cap? Also is it better to attach the PCV valve hose in the middle of the manifold between 1 and 2 carburetors of the three or in the middle of the back of the intake manifold? I am running progressive linkage on the three carbs. 0-70 on the middle carb, after 70 the other 2 pull in.  Motor has small performance  cam, aluminum Mummert Heads. 9.7 compression ratio and 40 over pistons.

The crank case should be sealed other than the Pcv. Including dipstick.

you need a vented breather for sure,with no breather at oil filter you would restrict oil drain to pan re high vacume in the valley.was involved with a young buck who lost the filler cap on a 302 and ducktaped the filler hole. resulting in a failed lower end due to poor drainback.

Agreed, the filler cap needs to be the vented type.

Ken,

On those three deuce intakes the ports on the manifold itself were never made for pcv plumbing although they all would hold a vacuum. The one in the middle was originally for the wipers and the one at the rear was for power brakes.

At issue is the "dirty" air from the pcv needs to be more evenly distributed among the cylinders. In the past I have run a pcv ported spacer on the middle carb. This will ensure you have no cylinders running lean. You may be able to get away with hooking up to the middle port on the top of the manifold but I would not recommend it. Remember too that back in the day these intakes were put on engines that had open ventilation and did not burn off the crankcase fumes.

Daniel Jessup

Lancaster, California

aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com

It's been a lot of years, but IIRC, the Offy manifold has the carbs on a plenum, and openings under the center carb to the lower plenum with the ports to the valves. Set up as a dual plane. That's why the Edelbrocks were somewhat more efficient. So the oil vapor ends up in the same place. I used the center opening for the PVC, and the back for the brake booster and the vacumn gauge.

Also, depending on your driving conditions and air cleaner, if you can find a filler cap with the sealed bottom and the tube on the side, run that into the air cleaner. On the filter side. Under high vacumn cruise conditions, it does a little better job of filtering the incoming crankcase air than the wire mesh in the open vented cap. And less oil smell in the garage. Fairly early on, we went to those closed systems, driven by CA air pollution laws, I think.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I would think the air being pulled through the crank case into the cylinder would glaze the bores over the crankcases reduction of drain back. Which is why there is a gauze filter between pcv and crankcase.
Yet now that I think of it there is usually a breather to the airfilter.

I would think the air being pulled through the crank case into the cylinder would glaze the bores over the crankcases reduction of drain back. Which is why there is a gauze filter between pcv and crankcase.
Yet now that I think of it there is usually a breather to the airfilter.

Thats the type system I have on mine. The original air cleaner I found to use already had the hole in it so I just used it. When we were forced to add the PCV system in CA some kits came with a block off plate for the road draft tube and others came with a tapered rubber plug to stick in the tube. Never had a problem with the PCV system but then they came out with the NOX device wich was a piece of crap..

Anyone know of the effects of vacuuming the crank case as I read something on pumps made especially for this to help the rotating components spin freer. I guess to much either way would cause issues.