[Bruce Edwards]

Not really sure what you are trying to do. If you are just trying to cool the air charge a bit put the dry ice around the carb and on the intake. You do not want CO2 getting in the engine. It will cut down on the performance. CO2 does not burn and you want to get a denser shot of oxygen.
Is the hood sealed to the carb? Getting cool air from outside instead of under the hood will make a big difference.
We built up a Ram Air system for our car that seals the hood to the top of the air cleaner base. Only outside air can get in and it is always cooler than under hood air.