[Grant Bowker]

I have two different PCV valves purchased recently.
One was sold by one of the MV (mainly Jeep) parts dealers out of the US. (If they are like most old Chev parts dealers all of the repro parts are made in the same factory no matter how they are packaged so I don't think the name of the vendor matters, in any case I'm puzzled not angry). This version is marked AC1543018 Ordnance 338400 and came in a box labelled Valve, assy WO-A6895 FM-GPW6769.
The other version was an ebay purchase that looked similar so I thought I would take a chance. It came in a box marked as AC Ventilation Valve CV-476 5747235 and repeats these markings on the valve.
Photos of both PCV valves are attached to this post and the next two. Both externally resemble the later production valve used on CMPs.
The description from the manuals is "In operation the high vacuum in the intake manifold at low engine speed overcomes the tension of the valve spring causing the valve to seat in the housing restricting the orifice. As the engine speed increases, and the manifold vacuum decreases the valve spring forces the valve off its seat thereby increasing the size of the orifice" (around the valve plunger).
My puzzle is that this makes perfect sense to me for the silver CV-476 valve but on the black WO-A6895 valve there is a drilling through the middle of the plunger body that to me would mean the valve is effectively always open, not just at higher engine speeds as described.
It also looks as if I could swap the CV-476 guts into the black housing to have both cosmetics and function, but I haven't tried this to see if it fits and functions.