Years ago, I found an SAE Transaction on a GM study they did on crankcase ventilation, circa 1961, when road draft tubes were the exit point for crankcase vapors.
There IS a particular flow rate for the valve. On the Chevy study, they used 1961 Biscayne 6-cyl cars in their plant security fleet (lots of low speed driving!!) for their test beds. In EACN case, the amount of condensate (which can make "acid" in the oil) was significantly decreased. Even more so with TWO valves. Internal engine cleanliness was significantly improved, without the condensate in the oil, clinging to the engines internal surfaces, worsening any sludge formation.
On a dedicated race car, the normal pcv system is deleted, replaced by Pan Evacuation Systems, using two 1972-style Chrysler crankcase air intake "breathers with rubber hoses attached, which then connect to one-way valves in the header collectors. No flow restrictors, other than the resistance of the Chrysler-style breathers on each valve cover. Helps horsepower.
As noted, the pcv system works with full manifold vacuum, usually via the primary throttle bores on a 4bbl carb. NOT just dumping into the intake manifold port. A Holley engineer mentioned that eh carb calibration compensates for the pcv flow.
I believe the most generic pcv valves are basically small block Chevy valves. There was a "purple color code" pcv valve for the earlier '70s L82 350 V-8. A bit more flow with the wilder L82 cam, so this can be a tuning tool of sorts if the engine has a pretty healthy cam.
With the pcv systems and the better motor oils of the middle '60s, engine life tended to increase by keeping the oil cleaner longer, which also aided in the longer oil change intervals which came later.
End result, KEEP IT operational. It helps things be better, on may levels! Especially in cooler/colder weather!!
CBODY67