[tom hand]

OK that was my first guess but here are a couple more. First check with a vacuum gauge and make sure the motor will hold 17 - 18 inches of vacuum in gear with the A/C on. If not the power circuit in the carb could still be the problem. If it will not hold that much vacuum, first use some carb cleaner and check for vacuum leaks. Spary the carb cleaner anywhere you suspect a leak and if the idle changes you found it. If that doesn't turn out to be the problem, try using the vacuum gauge to adjust the timing for more vacuum, I have seen many small blocks that the timing marks were not correct. In fact I would run as much timing as the motor will tolarate anyway because you will get better gas milage. Advance the timing till the motor "pings" under full throttle, then retard the timing till it just stops. This is usally the best setting for a sbc if the starter will tolarate it. Many times you can run 10 - 12 degrees btdc with premeium fuel. Last I have seen old vehicles have rust in the fuel lines that will go right thru a fuel filter. If this is the problem you will have stuff in the carb that looks like mud. The only solution for this is to replace the rusted component. I have run as many as three filters and still it will come thru. Good Luck!