1621 1973-1987 Buick Cadillac Chevy GM Olds Pontiac Grand National 196 231 350 4.5" water pumpFlowkooler high flow pump 1621 has a 16 vane CNC machined billet impeller. It is shrouded and ported and, with the increased vane count and a reduced impeller clearance, it really pumps the coolant. It achieves greater flow rates, higher head pressure and a more efficient flow. The impeller's 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