Holley 0-4777S Model 4150 Double Pumper 650 CFM Square Bore 4-Barrel Mechanical Secondary Manual Choke New Carburetor Mechanical secondary provides added fuel under initial acceleration and tire turning for lightweight vehicles Dual feed fuel inlet gives constant high volume fuel delivery 4-barrel carburetor with shiny finish Center or side-hung pivot float with adjustable needle and seat assembly Dual metering blocks allow fine tuning of secondary jets