I have rebuilt a Holly model G for a friend and several other NH's. I have a model S-2 that I will modify for a new needle and seat. The G and the NH I went with the double ball system and thought that was the best. They all stick and over flow and have to be tapped to stop. I know I would never have a T without a shut off valve for fuel right at the carb. The tank shut off is great but not for every day. What is the best needle and seat? I have even run a good amount of Marvel in the gas, but they still have the ability to stick. .......StucK...Bob
The ball valves have a bad reputation for the reasons you mentioned. I haven't used the new G valves and don't know how good they are, but I've had no trouble with the NH valves so far. Look here, and note Stan's comments:
http://www.mtfca.com/discus/messages/411944/497846.html?1417404199