Would love for that to be it but I can't figure out which line that would be. Weber carb so the vacuum setup is pretty limited. PCV into manifold. Brake booster into manifold. Valve cover vent into air cleaner. Vacuum advance into carb. That's about it to my knowledge. Unless I'm missing something or did something really stupid...
Also most of the higher viscosity oil have a green tint. It's hard to tell from the pics. If I were closer I'd be over there, that's one project I should have finished