If you are talking about the 3/16 inch tube that comes up through the head, through the brass fitting that connects the rocker shafts, and then bends and points back down to the head, I have LOTS of experience with this. I had my head rebuilt and the machine shop had rebuilt lots of 235s over the years. The guy that did the work has been doing them since the 60's. I asked him if he knew where I could get the original rocker arm shaft "oiler" assembly, and he said to leave it as is. The original design had the tube come up from the brass fitting and then bend down to just above the head. The end was slightly crimped with a center hole so that oil would spray onto the head and flow back down to the pan resevoir. However, since the old engines had partial oil filtering the little hole in the end of the tube pointing to the head would clog. As a result, oil pressure would build up and the pressure would be relieved by more flow out around where the rocker arms mount on the shaft. This was viewed by many as actually a good thing, so many garages actually cut the tube after it came out of the brass piece and folded it over permanently closing it. The oil still ran out at the rocker arms and still ran down to the pan. The only downside was slightly higher oil pressure. Again, some shops would only crimp the tube part of the way to address this "problem". Anyway, I cleaned up my old one, made sure that oil would flow to the rockers, and moved on. He runs fine.
P.S. Another way to reduce the oil pressure, per the guy that rebuit my head, err... engine head, was that some garages actually ground a flat spot on the rocker arm shaft the length of the shaft to ease the flow of oil out onto the head.
Hope I've helped!
