These carburetors that are intended for use with superchargers, and have a unique capability that allows their power Valves to reference the intake Manifold vacuum below the supercharger. This allows the power valve to operate as it should, based off intake manifold vacuum. A power valve provides further enrichment to the main metering system under load (low vacuum) conditions. Without this external referencing, the power valve would be reading the Supercharger boost pressure, which has no bearing on the engine load. Product Features:Tumble Polished Shiny Finish For Good LooksManual Choke For Precise Cold Start ControlDual Accelerator Pumps For Add Fuel Under Initial AccelerationDual Feed Fuel Inlets For Constant High Volume Fuel DeliveryMechanical Secondaries For Perfect Off The Line LaunchesLightweight Vehicles w/Auto Trans w/High Stall/Low GearingBoost Power Valve For Proper Enrichment Under Acceleration100% Wet Flow Tested By Holley TechniciansArrives Ready To Run
