Here's what I did with my dual-4V tunnel port manifold. It wasn't set up for a PCV valve, however the carbs could've been plumbed. But to avoid routing hoses to the carburetor bases, I drilled and tapped the manifold so it would accept a pipe-to-AN fitting. To that, I installed a 120-degree AN fitting with a push-lock end. At the crankcase side, I installed a well-baffled valve-cover
oil-filler cap fitted with a 90-degree fitting that would accept a hose. I then installed an inline PCV valve I found at the local NAPA store.
As trularin said, the outlet must be well baffled at the crankcase side, otherwise the system will draw a lot of
oil vapor into the intake system. This will result in high
oil consumption and blue smoke out the exhaust system. I experienced this until I found this ugly cap, but it works. I tried plumbing into the crankcase standpipe at the back of the engine, but it wasn't sufficiently baffled, which resulted in a lot of oil being drawn into the intake manifold.
One thing to be aware of is if your engine is on the lean side, an add-on PCV system will lean it out further. So be ready to rejet the carburetor/s to make up for the increase in air flow just in case.
