[Ross F-1]

One other thing to consider on Rochesters. There were two float needle valves, small and large. Physically the same size, but the hole fuel comes thru is different. Rebuilders commonly put the Large size in, I suppose just so they don't need to guess. Large valves were used in the later models made for bigger engines. But Large bore needles having the same float as Small ones tend to be less tolerant of fuel pressure. (more area times same pressure = more force trying to open the valve) Several vendors sell the Small orifice valves, for our engines they are the better choice.