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hi, the early AFB carbs didn't have weighted air valves above secondary bores. asfar as I remember, those were used up till 1966.
the 235 /273 had weighted valves starting in 1965. the 383 had none. lot of it depended on engine combo. AFB came out in 1960 ?? so you have early AFB carbs.

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Not so Pontiac, Ford and Mopar and other GM motors used Carter AFB, Aluminum Four Barrel starting in 1958, that had the weights on them Some of the smaller C.I. AFB carbs. did not have the weighted air valves under the rear secondary venturi boosters, but some did :shruggy :Most of the bigger C.I. motor carbs. had them stock The Carter Air Valve Secondary, AVS carbs, had the spring loaded door above the secondarys starting in 1968, maybe also the 1967 HP 440 motors, on the HP Mopar motors.