About 280. They rate two barrel and four barrel carbs at different vacuum levels, so you'll see lots of different answers to this, but the general comparable CFM is a bit less than 300. I have flow tests of several of these carbs, because they are used in oval track racing in the Street Stock class. The quickest way to find out if you need a bigger carb is to hook up a vacuum gauge and do a couple of full throttle runs with a friend watching the gauge. At higher rpm (4000+), note the reading, and if it is much above 2", you could use a bigger carb.
