Just about any carburetor will flow more air than its published CFM rating- - - - -it just won't do it at the manifold vacuum where the rating was calculated. The "Street Stock" racing class I built engines for at the Nashville fairgrounds 5/8 mile track required us to run a "350 CFM" Holley 2 barrel. A 358 cubic inch small block Chevy engine would run 6100 RPM on that carb before it ran out of breath- - - - -which calculates to 630-something CFM. The manifold vacuum would rise until the engine simply couldn't suck any more air through the carb, no matter what we did to cam, valves, or porting and polishing, etc.
The trick to running faster was to put 1/16" flat washers between the carb and the intake, and draw more air into the manifold without going through the carb venturi. The engine wouldn't idle, but it ran like a scalded cat!
A 305 engine with the same carb and some Sneaky Pete tricks on a HEI distributor would turn close to 7K RPM.
Jerry
