I have a 69 cougar with 351 windsor, and the the original 2bbl carb. The problem is everytime i rev it too high, or put a load on the engine in gear, it will backfire out the carb, and stall the engine. The firing order is right, the points and condenser are new, the dwell is at 29deg, and the ignition is at 12 advanced, and the idle speed is 600 rpm. The carb is unchanged as far as I know. Im running out of places to look to find the answer, and everyone i ask has conflicting opinions. I hate to start tearing the motor apart when the problem is something stupid. Any tips or advice will be well appreciated.