Pal - Pontiac had the Q-Jet option on the 230 in 1966 - 67; and the 250 in 1968 - 69. The 1966 carb would be the least desirable.
Truckedup - The problem with secondary bog with the Carte AFB generally lies with the air valve, as you guessed; however, weight (mass) of the valve is not the only variable. The angle of the airvalve on the aftermarket AFB's is designed for oversquare (high RPM) engines. Changing the valves to those from a high torque low RPM engine (ie. early 60's Pontiac) will generally clear the bog, assuming the carburetor is properly sized to the engine.
The following information is copied from our website:
"To help you pick the size carburetor for street use, consider the following Carter aftermarket carburetor sizes:
Square-bore (secondary is variable, based on engine demand)
400 CFM – 200 (P), 200 (S)
500 CFM – 225 (P), 275 (S)
600 CFM – 250 (P), 375 (S) (this is NOT a misprint)
625 CFM – 250 (P), 375 (S)
750 CFM – 375 (P), 375 (S)
950 CFM – 375 (P), 575 (S)
Spread-bore (secondary is variable, based on engine demand)
800 CFM – 200 (P), 600 (S)
850 CFM – 250 (P), 600 (S)
1000 CFM – 400 (P), 600 (S)"
Jon.
