bad city milage 2bbl

i would check your float on your carb i had a carter bbd on my super six set up i had poor performance and mileage i switched to a holley 2280 two barrel that also came on the super six i got 19 mpg that was street milage i had alot better throttle response its a really great carb that was with a 64 dart 904 3.23 225