Re: Crankcase ventilation routing
Because the crank act as a fan in the crankcase, the blowby gases (nasty stuff) exits though the PCV valve on the driver's side valve cover. The other valve cover is from where clean air is pulled into the crankcase under normal driving condtions.
I'm sure during higher blowby conditions (higher RPM or older engine, etc.) blowby gases can exit back into the air cleaner base from the pass. side valve cover where it's sucked back into the engine through the carb.
For street driven cars, I've always thought that having flow through the engine as Chevy designed, is better than breathers, because flow will remove the hydrocarbons, acids, and vapors, that will cause sludge, wear, and corrosion.
Also, keep in mind, not all PCV valves are equal. Engines with different vacuum levels need a valve to match. CV746C from AC-Delco is what I use for engines with limited vaccum.