Valve cover breather backward valve = no PCV?

1976 440-3 with smog eqpt and no cat. I have oil blowing out the dipstick. I took off the breather hose (passenger side) and sucked on the tube -- nothing. Took out the fitting and sucked on the tube -- just fine.

Also checked PCV valve (driver's side) and for any obstruction in the hoses. All good. I just passed smog and no cylinder appears to have blowby past the rings.

The question is if this could be the sole reason for lack of positive crankcase ventilation or if I should keep on looking.

Edit: Stupid rookie mistake. The parts store sold me a "breather" cap with a valve that only allows air out and allows no air in. Duh.

Dave it is always a good day when you can solve an issue yourself with minimal work. (enjoy it while it lasts!).

Put in a proper breather. No more oil out the dipstick!

Stupid rookie question, how can you tell if a breather is one way or two way?