Why would my PCV be buzzing?

[pnut]

Small block Chevy with Qjet.

MPCV valve is buzzing. The sound is like a radio controlled airplane engine (but quieter). I am sure it is the PCV, I pulled it out with the carb vac hose attached and the engine running, and could see the pellet "bouncing" off the the top from vacuum.

Is it simply bad, or do I need to use the back PCV port on the Qjet (On one of my previous posts this was mentioned).

Glad I bought the mechanics stehescope, it led me right to the PCV.

[TooMany2count]

wrong one for the amount of vacuum your pulling, had the same problem on a crate motor. went through about 4-5 before i got he correct one...joe

[65ny]

How do you tell if one is good or not??

[C9x]

Absolutely. They are different although they may look a like.

Remember also, just because one rattles, doesn't mean it's good.

Are they ID'd for vacuum level by the letter seen on the piston?

I pulled a 455 Buick valve and replaced it with an SBC valve since I required a 90 degree turn for the hose.
The Buick piston was marked with the letter "A".
The SBC was "E" or "F", not sure there.

I asked about vacuum levels, but that was a new one on the parts guy.
I settled for a generic brand and it's working well.
Better than the original Buick methinks.

The generic SBC valve probably doing ok due to the mild cam in the big Buick engine.

I took a look at a 400-M Ford Cleveland valve, but saw no markings inside.