Holley 0-1850S Model 4160 Street Performance 600 CFM Square Bore 4-Barrel Vacuum Secondary Manual Choke New Carburetor Features Next Gen needle and seat design to eliminate the need for external float level adjustment Single feed fuel inlet with vacuum secondary type Silver finish with side hung floats Manual choke for easy control of engine warm up Power valve blow-out protection with 2 full manifolds and 1 timed vacuum