Carb CFM recommendations
Yes, I get that. But those carbs had to be jetted down at the factory to match the limited airflow of the 318. Just because they made it work in limited production does not mean it was the best option. They simply had them on the shelf so they used them. But again, good point.
I don't want to beat a dead horse, but I find this discussion interesting. So I want to cover the jet issue.
Again, getting caught up in the math or the numbers can get you way into the weeds. I learned this as a kid tuning 2 strokes and I still see it today with 2 strokes and cars.
Never get excited about jet numbers, CFM number and such. IOW's, don't let a jet number or CFM number throw your thinking.
Any time you change a jet, all you are doing is altering the fuel curve to match engine air demand. The number on the jet is essentially inconsequential.
When the carb was designed, the engineer had to adapt the jetting, emulsion, air bleed, idle restriction (in this discussion) metering rod diameters and plunger spring ratings all have to be set to some generic numbers. You could be buying the carb to go on a 289 Ford or on a 480 inch BBC. Since the carb is self adjusting to a fairly large degree, the engineer will err on the rich side of damn near every jet/bleed whatever. Because being slightly rich to rich is better than being lean and cooking part.
So adjusting jetting to Mach your air flow curve has nothing to do with the CFM rating of the carb. That's one reason why Holley took (and still takes) such a beating about low speed driveablity, fuel mileage and such. Most of those carbs cam calibrated on the far right side of rich for most everything. Bleed area, emulsion and such were calibrated so if you had more compression and lots of cam and gear you wouldn't bolt on a Holley and cook the engine.
Carter didn't do that nearly as much. They were looking at a different market. The fact still remains that the fuel curve for any given carb as it comes out of the box is most likely never going to be correct.
So the upshot is just because someone has to reduce the jet area of a carb to correct the fuel curve doesn't mean the carb is too big. In fact, it's probably a good thing. The engineers sweat bullets about getting lean issues with carbs. So they over jet everything.
Again, just trying to paint a picture about NOT getting caught up in the numbers game.