1970 Chevrolet C20 Pickup - Motor Leaking Oil

[PbFut]

The 3rd photo on post 26 is of a factory riser, vent hose and flame arrestor. It's path is from the vent hole in valve cover on right side. The PVC valve goes in the left side valve cover hole. A PVC valve is inexpensive and best replaced if in any doubt on condition. Plugged will force crank case blowby up the the opposite side vent tube and grunge up your carburetor. Stuck open will cause a big vacuum leak making hard or impossible starts and bad idle. Plugging the right vent will limit air out of crank case into pvc. I do not know it this is good or bad. The pvc will pull blowby and flowing into intake to be burned is certainly better for pollution. I do not know if it has any power benefit or detriment. Replacing the riser vent tube with a vent cap can be done. Most vent caps don't filter like a engine air filter so there is that to consider.