I'm looking at buying a pair of AFB carbs. They appear to be a matched pair for a dual quad setup as one has a choke and air adjustment screws and the other one has no choke or air screws. One carb is a 3644S and the other one is a 3903S. Thank you for any help on this. Alan
Carter did not publish the CFM of virtually all original equipment carburetors. If the engineers for the car company were happy, then so was Carter. If one really wants to do one's homework, one can study the throttle bore sizes and internal venturi sizes of any of the AFB carbs, and then compare this to the Comp series and Super Street series carbs, of which the CFM was published. This will give a rough approximation, as casting differences in the Comp series and Super Street series versus the original equipment carbs with some of the air deflectors would marginally change the airflow. As an example of the above, Pontiac paid Carter to sabotage the AFB's used on the GTO's so the AFB would not outrun the more expensive tripower. 35 CFM was disabled (and may easily be enabled). As mentioned by Saltflats, one of your numbers is Chrysler, the other Buick. A concerned enthusiast would NOT use this pair as a dual quad set-up. If you are looking to put dual quads on the car in your signature, a pair of 1961~1963 Pontiac carbs 3300s or 3326s (you CAN mix or match these two numbers, depending on what you find) are calibrated very close to Chrysler calibration, and are much more common, thus less expensive than Chrysler AFB's. Unless you have a very radical camshaft, build the carbs stock, and then tune from the stock (baseline) calibration. Jon.
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