Steve,
Under the perfect scenario, a large air bubble would find the highest point in the engine to roost...this would be immediately under the thermostat. The little thermo-motor needs direct contact with heated coolant to react properly.
The small hole that is drilled in the flange allows this bubble to travel through to the tank, along with a limited flow of coolant, but insures the thermostat is surrounded by coolant.
This is how I envision it working, but between the Zanax and the Cutty Sark, I might be in Belfed's fog zone! :confused_smile:
Stuart
