Stage 3 - These pumps are assembled with exclusive Stewart Components 356-T6 heat treated aluminum castings. Designed in our cooling system research and development lab and precision machined on CNC machining centers. The fan hubs are 1/2" thick and machined from billet steel. These hubs are preferred by many top engine builders for lower vibration in higher RPM applications. Recommended for Moderate to heavy racing applications. All Stage 3 pumps feature: Billet steel fan hub, 1/2" thick with set screw for more positive positioning Exclusive Stewart 356-T6 heat treated aluminum casting Extra rigid cam stop with 3/8" adjustment screw (small block Chevrolet short castings) Precision ground fan hub for perfect pulley alignment. Equal flow to left and right cylinder heads. Precision impeller installed to exacting tolerance. Zinc plated rear cover bolt Extra material adjacent to block mounting bolts to allow drilling and taping of up to 1/2" NPT holes for installing external coolant lines to the center of the engine (small block and big block Chevrolet short castings) Higher flow and pressure for better coolingA full one-year warranty. Models with 3/4" ball/roller bearings offer five times the strength of standard bearingsPit Stop USA offers Stewart Stage 3 Aluminum Water Pump - 1970-78 Ford 221-351W and SVO SB 36113 at low everyday prices. Be sure to check out all of our products from Stewart Components including Stewart Components Radio Boxes and Stewart Components Small Block Ford Water Pumps.