2 questions. 1, is there a thermostat in the engine? Lack of a thermostat will cause too much coolant flow (due to lack of restriction) and will prevent the coolant from dissapating the heat. 2, did you set up a fan or blower to push air through the radiator. While the fan on the engine will move alot of air, it really isn't enough when the engine is run at speed. An ouside source of airflow is needed.
