[Dick Boneske]

Laws of physics tell us that the larger the orifice in the needle/seat, all other things being equal, the less pressure it takes to lift the needle off the seat.

A Tri-Power setup has three needle/seats controlling fuel into the carbs, not like a Quadrajet that has only one needle/seat. The amount of fuel allowed is three times that of a quadrajet, assuming the orifices are equal. Normally, the orifice in a Quadrajet is typically .135" vs the recommended center carb orifice of .101". But the two end carbs at .086" will allow much more flow than a single .135" orifice.

I use the Tomco needle/seat assemblies that have a flat rubber disc that shuts off fuel when the float exerts pressure on it. I am aware that many rebuilders frown on this style of needle/seat, but I've restored hundreds of Tri-Powers using this style of needle/seat with excellent results. In the past, there were similar flat disc needle/seat assemblies that often leaked and flooded the engine.

Previous to the late '90's, I used conventional needle/seats and had many instances of leakage, requiring disassembly of the carb to clear the problem. The rubber disc style needle/seat is not as prone to debris interfering with a perfect seal. I don't know why, but that is what I've experienced. Previously, with converntional needle/seats, flooding at initial startup was very common, occurring in about one out of three startups.