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Carter AFB for Studebaker
The Carter AFB (Aluminum Four Barrel) was the second four barrel carburetor produced by Carter, after the WCFB. AFB's appeared in 1957 and were used as original equipment on most makes of car at one time or another up to 1971. The last notable OEM application was as a dual-quad setup on 1971 Dodge 426 Hemi engines.
Interestingly, some Ford AFB's weren't made of aluminum at all, and were in fact cast out of zinc.
Carter AFB's were produced as the Carter Performance Series carbs until 1998. They are currently available as Edelbrock AFB carbs, which are produced by Weber USA. Most parts, including tuning parts like the jets and metering rods are interchangeable between the original Carter AFB's and the currently produced Edelbrock carbs.
Carter AVS - Dodge
The Carter AVS (Air Valve Secondary) is a refinement of the basic AFB design. Whereas the AFB used a velocity valve, which is a counterweighted flap below the secondary venturi, the AVS used an air valve, which is a spring loaded flap above the venturi. The purpose of the two is similar, but the air valve is adjustable from outside the carb.
When the throttle is opened so that the secondary throttle plates begin to open, vacuum develops under the air valve, slowly pulling it open. In this way, the air flow is controlled and the mixture is kept from getting too lean if the throttle is opened suddenly.
Carter AVS carbs appeared in 1966 on the 275 HP version of the Chevrolet 327, but were never again used on Chevies after that. AVS carbs were found mostly on Mopar applications from 1968-1971. The most sought-after AVS carbs are the 800 cfm models found on 440 CID motors.
Recently, Edelbrock has been marketing the Thunder Series AVS carburetor, again reproduced by Weber USA.
Carter did not build a performance version of the AVS after OEM production in the 1971 model year.