center tri carb won't idle...

[kip younger]

I'm putting tri power on a sbc 350 - got the first and third carb openings on the intake sealed off - only the center carb on the car. Just rebuilt the engine and put it together with a mild cam. The car will start and idle ONLY with the choke blade partially closed. If the blade opens completely, allowing full air flow into the funnel, the car shuts down immediately. My guess is too much air??? Not enough gas??? Wrong ratio??? There are no known vacuum leaks. I have backed the idle screws both out about 4 turns... hoping to get as much fuel as possible into the carb. How can I get the car to run on this 2 barrel? thanks - kip

should mention this is a rochester carb, with vacuum operated choke - thanks