It sounds like a vacuum leak to me as the prime suspect. Here are some other things to check since you said it was good on fast idle until you kicked the choke off. This indicates a lean condition on the run and several things can affect it. 1. Remove the covers from the metering rod vacuum chambers and start the engine. Best that someone else starts the engine as you observe. You will probably see the metering rod piston get sucked to the bottom on each side and then the engine does not want to run without gassing the throttle. Using a small screw driver or even a toothpick, raise the metering rod piston up and see if it changes idle quality. If an improvement is detected, it means that someone probably changed the primary jets to a smaller size or put in thicker metering rods - both scenarios greatly reduce the fuel flow to the idle circuit and not just the high speed circuit. The easiest cure is to stretch the springs under the metering rod pistons a little at a time until idle quality improves. Edelbrock also has tuning kits that include higher rate springs and their usage is based on engine idle vacuum. Do you have any idea what the engine vacuum reads when the 500 carb is on it and idling good? 2. The metering rod may be too fat for the orifice of the jet. It call for a smaller stepped rod or a larger jet. Of course the pesky spring is still in the mix! 3. The air bleeds in the primary boosters (brass skinny tubes that stick up and brass-bushed holes in the side) may be plugged. If they do not pass air, the idle mixture will go rich requiring you to turn in the idle screw to give it more air but then it uncovers too much of the idle transfer slot and that is a no-win situation. If the idle bleeds (the larger of the two in each booster) is too large, the idle mixture goes lean and again, you tend to set the idle screw up to get RPMs but enough fuel still cannot enter the idle system, the high speed system kicks in at the boosters and you gain nothing. Begin with the curb idle screws backed out 2-1/2 turns. Turn the carb over and adjust the idle speed screw until 1/2 of the skinny idle transfer slot is uncovered by each of the primary throttle blades. This is a good starting point. It is highly unusual for air bleeds to be a problem in these carbs! Did you buy this carb used and somebody that didn't know what they were doing messed with it? 3. It is flooding...but you will see fuel dripping from the boosters and it will be obvious. I seriously doubt this is you problem. Check these things out. I hope just increasing the metering rod spring rate starts you on the road to success. Good luck!
Pat
rayer:
