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Carter WCFB flow ratings

OK, so I misled you with the title, sorry.

To my knowledge (and what is available in existing Carter drawings), Carter published CFM for only one WCFB, the 2493s, a carburetor for 283 Chevrolet race engines. This carb was rated 380 CFM.

When the WCFB was produced, the method of comparing carburetor air flow was total venturii area. The first Competition Series catalogs published by Carter still listed total venturii area, while adding CFM ratings.

There is no doubt that if CFM figures were published by engineers, they would be more a more accurate measurement than total venturii area. But engineers test for CFM, and marketing personnel assign the published rated numbers. Anyone that thinks the engineers built carburetors to produce exactly "nice" CFM ratings such as 500 or 525 probably still believes in the tooth fairy! As an example, Carter flowed the AFB 3636s which produced 939 CFM at 3 inches of Mercury, and 1128 CFM at 1 1/2 inches of Mercury.

I have gone through the existing Carter drawings (I am the current caretaker) and calculated total venturii area for each one for which I have data.

For those that think about rebuilding kits, and tuning parts; I can assure you that, as of this writing, rebuilding kits with LEATHER accelerator pumps, main jets from 0.050 to 0.120 inch, original metering rods, custom metering rods, and different calibration vacuum springs are available for ALL of these carburetors.

So, listing by carburetor tag number within total venturii area (note the "s" suffix is omitted:

Area of 2.76 square inches: 2214, 2219, 2224, 2330

Area of 3.153 square inches: 2016, 2059, 2080, 2084, 2103, 2112, 2218, 2232, 2283, 2284, 2351, 2361, 2366, 2563, 3208

Area of 3.344 square inches: 2268

Area of 3.378 square inches: 2362, 2419, 2613, 2614, 2626, 2627, 3181, 3182

Area of 3.546 square inches: 894, 896, 932, 985, 996, 2005, 2041, 2053, 2072, 2082, 2088, 2109, 2110, 2119, 2126, 2142, 2143, 2181, 2185, 2186, 2210, 2253, 2302, 2303, 2317, 2365, 2432, 2444, 2445, 2474, 2476, 2530, 2552, 2553, 2628, 2725

Area of 3.559 square inches: 2505, 2555, 2574, 2575, 2576, 2631, 2632, 2633, 2634, 2635, 2636, 2655, 2669, 2761, 2762, 2819, 2829, 2830, 2831, 3059, 3165, 3166, 3167, 3205 (this is the size rated 380 CFM)

Area of 3.761 square inches: 2394, 2534, 2535, 2582, 2584, 2590, 2593, 2656, 2657, 2690, 2691, 2692, 2853, 3696, 3697

Area of 3.988 square inches: 2255, 2266, 2267, 2354, 2355, 2543, 2544, 2545

Area of 4.43 square inches: 2197, 2311, 2314, 2333, 2334, 2347, 2358, 2364, 2367, 2370, 2371, 2372, 2373, 2404, 2442, 2443, 2532, 2588, 2589, 2622, 2660, 2698

Area of 4.479 square inches: 2220, 2265, 2246

For reference:

Carter Competition Series AFB 4758s (500 CFM) has a venturii area of 4.67 square inches

Now, doing some mathematical speculation:

If one compares the rated CFM against the measured venturi area on the 2493s, one arrives at a value of 106.8 CFM / In²

If one compares the rated CFM against the measured venturi area on the 4758, one arrives at a value of 107.1 CFM / In²

So if one wishes to come up with an APPROXIMATION that is probably better than most internet guesses, one may multiply the venturi area listed above by 107 to come up with a figure.

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