Positive Crankcase Ventilation didn't come out until the late 50's early 60's, until then a breather pipe was used in all engines. Piston that goes up creating compression also goes down into the crankcase doing the same thing, but in the crankcase plus piston ring blowby.
Taking your foot off the gas and using vehicle inertia to slow you down, did exactly the opposite, creates a vacuum in the crankcase to suck up dust and dirt off the road. Ha, when overhauling an engine in these cars, needed a shovel to pick up all that muck in the crankcase, and also in the valve covers with overhead valves.
When you did hit the gas with an old engine, black smoke would pour out of the breather pipe, who cared, engine still ran, would see many vehicle on the road like this.
So that breather pipe was replaced with a hose, going from the crankcase back into the intake manifold, on an OVV engine, also opened to the crankcase, this is where that hose was placed. But have a situation where the intake manifold pressure was greater than the crankcase that would blow the air/fuel into the engine oil, not good, so a check valve was installed to prevent this, flow can only occur from the crankcase to the intake manifold. And this is all that a PCV valve is, a check valve.
Ha, guys would shake it, if it rattled would be okay, not very bright, right way to check it was to blow into the direction toward the intake manifold, should blow free, other way, should not leak at all. Use to be a one buck valve, but since it was carrying all the crap from the crankcase, would get sticky, a blast of choke and carb cleaner would get it working again. Was good to do this every couple of thousand miles or so. Or your engine oil would be deleted with gasoline, not good either.
Is there a better way? Apparently not after some odd 50 years. Keeping your engine clean with Seafoam does help, still get carbon buildup on the piston rings, letting more blowby get through. And returning this crap back into the intake manifold really wasn't that bad until they installed fuel injectors, that crap builds up on the face of the injectors affecting the spray pattern. In this respect, carburetors had it all over fuel injectors. If the return was to the base of the carb, some brains thought it would be good to return that hose to the air cleaner, that really messed up the carb with crap.
GM for years was a little smarter in returning that hose to the base of the now throttle body, but don't feel they were very wise in returning this hose actually after the air cleaner and directly into the turbo, Already had a sticky vane in my TB, was very slow in closing when I released the gas pedal, had to clean that with choke and carb cleaner and appears to be a periodic job.
Wonder if the engineers that did it this way are reading this, apparently they are not aware of the 55 some odd year history of this valve. The PCV valve was metal, cheap using just a plain neoprene hose. Corrugated plastic when you think about it is nothing short of stupid, restricts air flow. And 70 bucks for this POS is nothing short of outrageous, and becomes very brittle in cold temperatures.
This is definitely another item that should be added to that 150,000 mile/10 year warranty like they did on several other items.
And yes, this PVC is pulling 19"/Hg from the crankcase, actually from the camshaft cover, same thing, and will also pull some engine oil from it. And yes, this oil is getting back into the combustion chamber causing a chain reaction even further adding more carbon build up to the piston rings, really a very nice self destructive mechanism.
Find it a lot easier to discuss issues like this to other engineers, oh, I didn't think about this, worse people to discuss issues like this is to marketing and your Chevy service manager.
