Some people get confused over how much air the engine needs and how big the carb should be. If you know how much power the engine is going to make then you can calculate how much air the engine will consume to make that power. For example, a 600 hp engine will consume roughly 850 cfm of air at peak power. So that is the easy part, the harder decision is what size carb to buy. Obviously a 850 carb would work but so would a 650, 750, 950 or 1050. The different carbs will work differently with the smaller carbs working better at low speeds while the bigger ones are better at WOT.

So the answer is "it depends" which is the same answer to most of the questions on here. You would need to provide some specifics on the car and engine and how you are planning to use it to get a better answer.