Crankcase ventilation.
My 65 273 in 1969:
Air gets sucked into the breather, blows out through the pcv.
Before the pcv, there was the road draft tube, which just expelled the vapors under the chassis. Worked best when the car was moving.
I have three sixties Mopars with an open breather/oil cap on one side, pcv on the other. Never had oil residue on my valve covers. Except when my high mileage 340 had five broken rings. :eek:
My 65 273 in 1969:
Air gets sucked into the breather, blows out through the pcv.
Before the pcv, there was the road draft tube, which just expelled the vapors under the chassis. Worked best when the car was moving.