That really depends on what year 302 you are talking about, the condition of the engine, state of tune, etc. Your carb may be a little big. I wouldn't go over 600 cfm on a 302. A small engine needs velocity (actually all engines) as much as, if not more than, volume for the sake of volume.i have a 302 with long tube headers connected to a flowmaster exhaust, electronic ignition, a holley 650 with spacer. How much power am I making and what would porting and milling down the heads do for the car power wise? Thanks!