Leather et al,

Saying thet slower flow thru the radiator will give more cooling is like saying a lower wind speed will give less of a chill factor.

The hotter the radiator, I.E. the faster the hot coolant is flowing thru it, the more BTU, or calories for you that are metric oriented, the radiator will dissipate. That's why a water pump is used. Thermosyphen will not move the coolant fast enough to cool engines burning more fuel.

P E H