Edelbrock's Annular Flow Booster technology brings superior fuel atomization to all high-horsepower small- and big-block engines with the AVS2 800 CFM Manual Choke Carburetor #1912 that is specially calibrated to make power. Annular Flow Boosters deliver near EFI-like drivability that you can feel as soon as you step on the gas. Fuel distribution is refined by eight equally spaced orifices in the booster rings that replace down-leg boosters which simply dump raw fuel into the venturi. Flat spots are completely eliminated and throttle response in the low- to mid-RPM range is improved tremendously without sacrificing that top-end power that Edelbrock is known for. The AVS2 is unaffected by engine backfires since there are no power valves to blow out. For fast and simple part-throttle tuning metering rods and springs can be changed in seconds without carburetor removal or fuel draining. AVS2 carbs have the unique ability to "hold a tune" when compared to other carburetors. Your tuning and adjustments stay unchanged so performance remains consistent. Updated primary and secondary booster clusters in the AVS2 offer the most accurate and up-to-date calibration available for today's fuels and octane levels. Additionally the unique Qwik-Tune Secondary Air Valve allows for limitless calibration of the secondary circuit. Adjustments can be with simple hand tools in seconds to suit your application. The AVS2 features a two-piece ease-of-tuning design that lets you make float level adjustments or replace internal components without draining the fuel from the carburetor or removing it from the engine. The AVS2 800 CFM #1912 comes with a manual (#1912) or electric (#1913) choke in satin or chrome-like EnduraShine finish. All AVS2 Series carburetors like Edelbrock's popular Performer Series and Thunder Series AVS are designed manufactured assembled and calibrated by Edelbrock in the USA.