New PCV Valve whistles

I just installed a fresh 318 in a Dart and got a new PCV valve from NAPA (Standard part). The thing whistles when the engine is running. It's so loud I can hear it in the car at 50 mph!!! So I switched it with the old, but completely functional valve from a different 318 - no whistle. I put the new PCV in the other car and it whistles there too. So I took the PCV back to NAPA, they replaced it with a new one that DOES THE SAME DAMNED THING!!! So I went to a different parts store (Advance Auto) in a next town and bought another PCV - and DAMMIT IT DOES THE SAME THING!!!. Any thoughts on the problem? Any suggestions for a source for a valve that is better quality?