Back in the day I put two 650 CFM AFBs on a 347 Pontiac with a hot cam, headers etc. A pair of 600s came stock on superstock 409s. That was way too much. The guy at the speed shop said of the counter weights holding the secondaries closed until there was enough air flow, "Don't take em out." Of course I did, only to put them back in a week later.
Do a calculation on the air requirement for a 235 assuming 100% volumetric efficiency at the maximum anticipated RPM: Just for drill let's say 4,000 RPM. (crunch, crunch, crunch) OK here it is -- you'll need a whopping 272 cu. ft. per minute. I don't know exactly what volumetric efficiency you can pull from a hot 235 but it's way below 100%. So the issue with old inline sixes is not air flow but mixture distribution. Typically the end cylinders get a less dense charge than the center cylinders. That's why hot rodders of old used the two or three single bbl carbs. I'm not dissing AFBs they are an efficient carb and can be tuned to get excellent performance and economy but you still haven't solved the mixture distribution problem. Mopar took a good stab at it with the slant six. Compare its manifolding to a stock I-6 Chev or GMC. Night and day. Four bbls. on a slant six worked very well but the hot dogs still used multiple small carbs on the Chevs and GMCs. A friend from the Wayback Machine had a 53 Chev business coupe with a 1/8 over 270 jimmy sporting 5 Stromberg 97s and tube headers. It would blow the doors off another friends "Duntov" 283 V8 55 Chev coupe. One thing in their favor is that AFBs don't leak, neither do Holleys. By 1965 virtually all Stomberg 97s did.
If your vacuum gauge will hold 0 in. Hg at full throttle at top RPM, that's all the carburetor you need. My truck's 235 will hold about 2" vacuum at full throttle at 3,000 RPM on a hard 3 mi. 6% pull at 4,000 ft. elevation. That takes about 5 minutes and I wouldn't want to push it any harder 'casue there's another hill like that a couple miles further on. I have two little Zienith 228s on an Offy manifold with Fenton Headers. On a warm day (72F) the oil temperature will be about 220F at the top of the hill. Water temperature @ 180.
