Originally Posted by 78 monte
You have to have suction out of the engine and a fresh air return into the engine.
Normaly that would be a PCV valve in the front of the drivers side valve cover and the pipe(factory)from the air cleaner to the passenger side valve cover.....If thats what you are talking about,you can replace the pipe with a open air breather.
As far as "oil breather cap" the old motors had a road draft tube at the rear of the block that went to the underside of the car using the under car air turbulance to suck out the crank case fumes and the fresh air return was at the vented oil cap on the oil filler tube.
The road draft tube on old motors did not work by "under car air turbulance to suck out the crank case fumes" It was the pressure within the engine that pushed the fumes out. The fumes escaped even when the vehicle was parked and the engine running. It was also the way water in the crankcase was allowed to evaporate out of the engine.