Cast aluminum 3-groove V-belt crankshaft pulley for use with 55-68 Small Block Fits Chevy short style water pumps. Precision machined aluminum construction. Lightweight and strong. Three grooves for 3 V-belts. Mounting surface to the center of the first pulley groove 0.34" Mounting surface to the center of the second groove 1" Mounting surface to the center of the third groove 1.59" Pulley width 1.94" Get the correct pulleys for your application by learning which water pump you have as explained in our tech article. SBC - Short vs Long Water Pump. Item Details Triple Groove, 6-3/8" Diameter