Best way to do Positive Crankcase Ventilation?
 

Okay, I've got another thread on Club Cobra asking about vacuum port location for the power brake booster. I've got a new bigger KCR 445 sbf and have driven only 5 miles and experienced the dip stick popping up slightly and oil misting the engine compartment. Looked a little wet in the areas of the breathers on the valve covers also. I will be running a pcv valve from the valve cover to a 3'8" barb at the base of the carb. Then I was going to use a breather type cap on the other valve cover. Well, I got to reading (until 2am in the morning) about different systems such as the crankcase evacuation systems, etc. and they all have their purpose for specific driving purposes whether drag or street. I found some notes from a Speed Shop in California written about 12 years ago and seems to make since and I recall many of the 70's cars had this setup and probably still do. I'll write an abbreviated version and would like input on if this may be a good way to proceed with my pcv situation:

I haven't seen anybody address the issue properly and I hope to shed some light on the history of PCV systems. PCV systems have been around since the 50's, starting with road draft tubes and finally becoming today's type 4 systems. To correct earlier posts. It's true the header check valve system only works when you have enough exhaust flow to produce a negative pressure on the valve therefore sucking the crankcase vapors and pressure out of the engine block. Obviously this is achieved by revving the motor. A type 4 system does the same thing. 1st of all the PCV valve works at idle or whenever there is high vacuum. It doesn't take much (6" or so). The vacuum pulls the crankcase vapors into the manifold (usually from the carb base to one of the valve covers) and burns it. This will not hurt even the highest of horsepower engines. Now the other side of the coin everybody is failing to point out is the breather side. The other side (other valve cover) of your engine should have a 3/4" tube going from a chrysler style closed breather to the bottom of your air cleaner. This can be connected to the air cleaner base via a 3/4" elbow available at any speed shop. Now this part of the system works like your race/header/check valve system. The air rushing into the air cleaner at wide open throttle produces a negative pressure or vacuum on the 3/4" hose going to your chrysler style closed breather at the valve cover, thus pulling crankcase pressure an vapors into the air filter housing. All cars today (this was written in 2000) use this system and is very effective.

I recall my 70 model Corvette PCV was plumbed this way and I looked up in Ecklers Corvette parts and you can get the elbow for the base of the air cleaner and the elbow going into the valve cover for a few bucks. So do I run my PCV valve to the base of the carb and plumb the other valve cover to the air cleaner so you have positive crankcase ventilation at all times or is the typical pcv valve at one valve cover and breather cap on the other valve cover suffice? May not look as nice but I want what is best, Thanks.

The simple breather on the opposite cover works great . The initial reason to route the breather to the airfilter is to make sure that the air going into the crankcase is clean and filtered.
The air is sucked in the breather through the engine , out via the PCV and into the intake. In other words , as a seperate system , very simply in one side out the other making sure that what goes into the engine is clean. The PCV. Should definately be connected to the plenum and not a runner.
John

Thanks Chanmadd (John)

What are the weber guys doing?

...adjusting.

A little fine wine in moderation today Jamo??;)

Have been beating myself up on how best to ventilate the crankcase on the new Aluminum Donovan sbc with Nasca SB2 topend.Seriously thinking about a vacuum pump for a cleaner setup,only need one hole in one valve cover to make it work.This motor will be replacing a 23*head sbc in a motorcycle so looks is important.Still researching the subject.

A Vacuum pump is the best method but extra components to think about. I don't particularity like the plenum set up that most of us, me included use. It's a small air leak at idle that raises the RPM's and forces me to close my throttle blades. Then when I raise my initial timing to where I want it that raises my RPM's making me close them even more. So it factors into tuning. One day I will remove the plenum PCV and fix everything, I'm just not sure how I want to go about this.
Can anyone give me some parts and a simple working plan?

I thought most air cleaner PCV arrangements go INSIDE of the air filter element of the housing, not outside. I run a PCV off one cover to the base of the carb on the rear (which it was designed for) and run a breather on the other. My air cleaner housing has a boot covering the PCV inlet which is inside off the element (not filtered). You can see the PCV off to the left here going to the carb base and the breather on the upper right on the other valve cover.

http://www.ffcars.com/photopost/data/500/DSC01328.jpg

Yes, they pickup the air from inside the airfilter, most have the little guaze filter. The breather itself is an oil type air filter, like a K&N type, wich is perfect, to make sure the air entering the crankcase is filtered.