To determine Carter AFB carb flow, measure the butterfly bores and use the table below:
CFM Venturi Diameter Bore Diameter
primary secondary primary secondary
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400 1 1/8 1 1/4 1 7/16 1 7/16
500 1 3/16 1 1/4 1 7/16 1 11/16
575 1 1/4 1 9/16 1 9/16 1 11/16
625 1 3/16 1 9/16 1 7/16 1 11/16
750 1 7/16 1 9/16 1 11/16 1 11/16
9000 Series AFB Code Deciphering
Base part number is 9000 and the last three digits refer to flow rating. For example, 9625 is a 625 CFM AFB carb. Adding 0, 9625 means it was set up for a Chevy style linkage, adding 1, 9626, means it is a 625 for a Chrysler, adding 2, 9627, means it is for Ford; adding 10, 9635, means provision for EGR.
If the carb is an aftermarket version, it will have a 9xxx cast in the front near where the mounting stud goes through.