Okay, so I installed the two chrome caps into the holes on my new valve covers. Now, I took it to the mechanic, and he says that I'm missing the PCV. I had it hooked from the right side cap into the bottom of the carb. He says there there is a big time vacuum issue with the way I have it set up.

My main questions is how do I know what type of system I have: vent tube, positive or closed? I was looking through the shop manual, but I can't tell what type it is.

Do I need to just stick the PCV Valve into the right valve cover and get rid of the chrome thing?

 

You should have a PCV in one of your "chrome things" with a hose running to the large PCV manifold vacuum port on the carb. The other side can be a filtered cap or you can hook a hose up to the air cleaner. You just want filtered air entering the crankcase. The idea is air enters the crank case through the filter and exits through the PCV at a controlled rate so that the crankcase has some positive pressure and you do not create a vacuum leak at the manifold. The PCV basically allows some crank case pressure to build up before recycling it into the manifold. Without a functional PCV, you will have a vacuum leak because the carb will not be able to build manifold vacuum due to the open port that is your non-functional PCV. Example, suck in through a straw, then suck in through a kinked straw. You will get more vacuum with the kinked straw. The moral of the story is run a functional PCV and filter the air entering your crankcase.

If you do not run a PCV, you need two filtered cap and need to plug the manifold PCV port on the carb. I am not sure why you would want to do this because the PCV help prevent blowby, but if you want to plumb it that way, you need to filter it and plug the vacuum port.

 

I have a minor disagreement with that. The PCV doesn't create positive pressure...it vents it, thus preventing it. Otherwise you would be blowing gaskets. I don't think it prevents blow-by either. Other than that, I agree with what you said.

 

Useful discussion. What i need is a side mount PCV valve as my high rise rocker covers are
too close to the export brace

Jav

 

OK, I was a little off when saying positive crankcase pressure. It does restrict air flow from the crankcase to the carb depending on vacuum levels to prevent a vacuum leak affect. Without it, you basically vent blowby into the atmosphere and Al Gore will hate you. By preventing blowby, I ment venting blowby, which is the purpose of the PCV recycle system. Most all engines have blowby, but the PCV system keep the gases from blowing out of your engine.

From Wikipedia:

"The Positive Crankcase Ventilation valve, or PCV valve, is a one-way valve that ensures continual evacuation of gases from inside a gasoline internal combustion engine's crankcase."

"The PCV valve is only one part of the PCV system, which is essentially a variable and calibrated air leak, whereby the engine returns its crankcase combustion gases. Instead of the gases being vented to the atmosphere, gases are fed back into the intake manifold, to re-enter the combustion chamber as part of a fresh charge of air and fuel. The PCV system is not a classical "vacuum leak." All the air collected by the air cleaner (and metered by the mass air flow sensor, on a fuel injected engine) goes through the intake manifold. The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back in to the intake tract again. It is an "open system" in that fresh exterior air is continuously used to flush contaminants from the crankcase and into the combustion chamber."

"The valve is simple, but actually performs a complicated control function. An internal restrictor (generally a cone or ball) is held in "normal" (engine off, zero vacuum) position with a light spring, exposing the full size of the PCV opening to the intake manifold. With the engine running, the tapered end of the cone is drawn towards the opening in the PCV valve, restricting the opening proportionate to the level of engine vacuum vs. spring tension. At idle, the intake manifold vacuum is near maximum. It is at this time the least amount of blow by is actually occurring, so the PCV valve provides the largest amount of (but not complete) restriction. As engine load increases, vacuum on the valve decreases proportionally and blow by increases proportionally. Sensing a lower level of vacuum, the spring returns the cone to the "open" position to allow more air flow. At full throttle, there is nearly zero vacuum. At this point the PCV valve is nearly useless, and most combustion gases escape via the "breather tube" where they are then drawn in to the engine's intake manifold anyway."

 

I have seen some Chevy big block drag cars with sealed rocker covers and a threaded gas escape system on the front side (PCV system). You will need to add the hole, but something like this may work.
http://www.cantonracingproducts.com/...ion&key=65-300