Tri Power was designed to work as a primary/secondary system. The primary carb is the the center one. It is the only one with a choke and the only one with a idle circut(because the engine runs on it exclusively at idle and off idle). It's just like running a 2 barrel. The secondaries are the end carbs and they are design to operate only when you got your foot in it just like your 4 barrel. There are no chokes,no idle circuits,If your carbs have idle circuits you will have to plug them. The throttle shaft is also different because it has to accept butterflies that are twice as thick as the primary butterflies.