So, where does your engine ventilation come in from? Doesn't look like anywhere. So the vacuum of the intake is going to draw that from the engine/oil area through the PCV.
Early SBC breathing was in the ventilated oil filler cap and out the road draft tube.
Where do you put oil in at? Maybe you need to put in an oil filler (ventilated) cap on the opposite valve cover while still maintaining your old school look?
