My 84 has a oil filler on the valve cover that has an extension which appears to be some sort of breather for the valve cover. Can it be replaced with a regular oil fill cap or does the stock cap provide some type of vent for the emissions?

 

one valve cover should have a pcv hose going into the intake, the other should have a breather. If there isn't a seperate breather then I'd leave the one on the filler neck.

My valve covers don't have a oil fill cap, just the breather and pcv, so I have to yank the breather out to add oil.