Old School Valve Covers

BTW, whatever PCV valve you use, search around to see what vacuum level the valve opens from the low flow idle setting to the high flow setting. If you have a cam that lowers the vacuum level at idle, a lot of stock PCV's will be at the wide open setting at normal idle, which they should not be, and that will dump a lot of air into the intake. That makes carb tuning more difficult in idle to low cruise transition, since when at low level cruise, the vacuum level will go up and the valve will close down, putting less air into the intake. That 'backwards' air flow change into the intake is not what the carb is set up work with.

For example, the stock Mopar PCV opens up to cruise flow at something like 14-15 in vacuum.... using one with a cam that drops the idle vacuum to a lower level can result in these issues.