I was wondering if anyone could answer this question.. I can't seem to find any technical info on size, opening spring pressure in a pcv valve.. I have one pcv in each motor..Looking at the bottom where the plunger moves , one has a number 16 stamped on it.. (does this mean 16" of vacuum) and the other has the letter A .. It seems that these pcv's have more resistance on the plunger..after i took a screw driver and pushed the plunger in ... I didn't know if these were correct for my 502 carb motors so I order 2 for my specific motors.. After hooking them up I noticed they were wide open at idle..and were causing a rich stalling loading up kind of senario. The plunger had very little spring tension.. I removed them and motors both idle smooth..
Ever since i used a pcv valve system i have no white gunky stuff under the valve covers or on the filler cap..I just want one that doesn't open all the way at idle so it won't cause a idle problem while in gear..My vacuum reading is 14.5

thanks