Small Block Chevy Cast Alum. Long Pump Double Groove Lower Pulley

Speedway Cast Aluminum double groove pulleys for Small Block Chevy feature a 20% reduction. Reduction pulleys have a smaller diameter which slows the speed of your fan, water pump, and alternator to reduce drag for more top-end horsepower. Plus, high RPM water pump operation is improved due to reduced fluid cavitation. This is a 25% reduction pulley when used with the correct upper pulley, part number 91015476. Machined from lightweight cast aluminum. Superior belt retention with extra-deep grooves. 20% reduction slows accessories down for less drag. Adds top-end horsepower. Reduces water pump impeller speed below cavitation threshold. Improved high-RPM cooling capabilities. 910-15488 5-7/16" O.D. Available for long water pumps. 5/8" shaft. Note: The lower crank pulleys are manufactured thicker than normal stock pulleys.  This requires longer 3/8" bolts to be purchased separately.  Allen head type bolts recommended.  Item DetailsCast Aluminum Lower