A PCV is not a one-way valve and never completely closes. A tapered cone moves in & out of an orifice (sized for engine displacement) balancing engine vacuum against an internal spring. It should rattle when shaken.
At high vacuum the cone retracts, allowing full vapor passage. At WOT the vacuum drops and the spring moves the cone tip deeper into the opening and restricts flow.
If you can't find the right one, a PCV from a similar engine such as the Gen-3 230 or 250 should be close enough to work.
