I wonder if the early PCV setup was also to prevent fumes from getting into the cab with the forward control models and the COEs, seeing as how the engine was directly below.
I put a PCV system on my 51 this year. I think it is a little cleaner even sitting there idling. I have a theory that the blowby from the early high pressure combustion pushes some unburned mixture past the rings and maybe it is a little worse than the normal exhaust.
