What size carb?
there is a good formula for this
(engine displscement (c.i.d.) X max rpm) / 3456 = ideal carb cfm
**example
360 X 6500 / 3456 = 677.08
this formula gives you a good base line to start then you can estimate for larger cams heads ect. this formula assumes 100% volumetric efficiency where we probably only see about 80%V.E. in street engines, so in mild street apps. use only 80% of your total and round up to the next whole cfm number in this case it would be 550-600