A stock thermostat is calibrated for a stock water pump speed. Spin the pump harder and coolant pressure starts pushing the valve around, so the engine never settles at one temperature. This one is built to hold its calibration under that pressure and flow enough to keep a hard working engine stable.

Mr. Gasket 4365 High Performance Thermostat Features:

• 195 degree opening temperature.
• Designed to resist large variations of coolant pressure at high rpm.
• Opens fully at the correct temperature consistently regardless of engine rpm.
• High flow design suits engines operated at sustained high rpm.
• Sold individually.