With the new Shaw t-stat featuring a smaller opening and less opening distance than the OEM style t-stat, it will change the coolant flow balance between the radiator and recirculating through the engine.
The radiator bypass from the intake manifold coolant crossover to the water pump through the timing cover must have 'balanced' flow with what coolant actually passes through the t-stat and into the radiator.
Increasing the t-stat restriction will reduce the flow rate through the radiator somewhat, but will INCREASE the flow rate through the engine.
I would guess that in your case the Shaw t-stat made for a better flow balance between engine and radiator. For the most part, increasing coolant flow helps with cooling (up to the point to where you're getting enough turbulence to cause severe cavitation and reduce the flow rate), and you have to use the limited flow you get from the water pump wisely.
|