I recently was trying to swap a pcv valve into an engine I am building and after I broke the old, brittle plastic thing, I bought a new one from napa auto parts and noticed that I could blow air through it both ways. So it will work for n/a, but under boost it will pressurize the crankcase, forcing air into the breather box on the back of the block and up and out of the vent on the valve cover, probably taking a considerable amount of oil with it.

I then checked an old oem valve from my 87 accord, it is a nice, quality metal piece that will never break and can be easily cleaned, and it seals pefectly when you try to blow through it from the manifold side. Obviously this is the valve that I will be using..

So is my new valve defective, or is that how the newer ones are, or is it just that this is a $10 part from napa and not oem? How many of you boosted guys actually checked your pcv valves for one way only function?