1620 1962-1966 Buick 401 425 Nailhead water pump for AC carsFlowkooler high flow pump 1620 for the Buick Nailhead has a CNC machined billet impeller designed with an increased vane count and a tighter impeller clearance. It achieves greater flow rates, higher head pressure and a more efficient flow. The impeller color is due to Type II Class II military grade surface coating which protects against corrosive fluids. FlowKooler introduced the first hi flow pumps and continues to improve impeller design. Why is