If I remember correctly Tom Langdon told me that the H-W 2 bbl was rated at about 260-270 CFM FWIW. He also told me that running two of these could not be compared to a Holley 4 bbl @390 CFM because of the way the 4 barrels are rated using different parameters. He said it ran better milage than a one bbl but had the extra power of an additional carb available because it's progressive. Now how does that compare to the original Rochester? Sorry, I don't know.
But if I were only running one carb I would want it to be this one I think.
