1677 1996-1999 Chevy GMC HUMMER 6.5L Diesel CCW water pump - bolt on pulley

The 1677 is designed to outperform GM's higher flow rate "130 gpm" pump released in late 1996.  GM grew the impeller diameter by 10% to outflow their earlier pump designs versions and utilized a dual thermostat design to increase the flow rate and to prevent pressure surges within the cooling system.   Thermostats Our impeller outperforms and outflows to help the 6.5L diesel run a little cooler under a load.  The impeller has an increased vane count, a reduced impeller vane clearance to the casting volute, a more open eye to permit greater flow and a ported shroud to build pressure in the eye and an appropriate B gap clearance to limit the potential of pressure pulsation or hydraulic shock.   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 incr