Which Two-Barrel to Use?

pishta said

The 350 would be a great size, actually a little big as the 225 will never pull 350cfm. It may pull about 270 on a great day with some head work.

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I just looked at my notes from the hotrod.com article from 5-18-2017 where they dynoed a slant six. Stock hp was 130.2. First step up was swapping on a Carter 2 barrel BBD rated at 260 CFM. HP jumped to 151! That's an increase of 21 and no other change after that netted as much of an increase.
Next change was Dutra duals with an increase of only 11 hp.
Eventually they went to an Aussie Speed intake and a Holley 390 for 177 hp before they broke. IIRC they blew a head gasket.