Don't remember what they were rated at stock, somewhere around 300 CFM for the big one, maybe 250 for the ends. Still more then enough CFM to support a 400 or 455 Poncho.... Back a zillion years ago, Arnie Toftland and a few others ran NHRA Super Stock with the tri-powers, they were in the high 10's, low 11's way back then.... Some of the circle burner carb builders have some modified Rochester 2 bbls. that will flow enough to run a single carb on alcohol though....