If I had a downdraft tube with an oil fill cap on it, I would put a breathe cap on it as an inlet for fresh air for a PVC set up which would draw the fumes out of the engine via a PCV valve in the valve cover. I would of course need to block off the lower end of the downdraft tube.
I realize that this is backwards as to how the original PVC was setup for these engines, but I have always thought that the engineers had it backwards to begin with.
To be fair to the engineers back in the day, there were very few paved roads back when these trucks were new, so the location of a breather cap on a downdraft tube would not be drawing much "fresh" air that close to the dirt roads.
Last edited by 52Carl; 10/03/2025 11:45 PM.
