With no thermostat the water pump is the limiting factor. The pump will push all the water out of the engine in a couple seconds if you remove the top hose. The water needs to stay in the engine long enough to absorb heat and in the radiator enough time to get rid of it. If it circulates too quickly it just goes round and round. The block and head overheats because the water cannot absorb it. The oil thins out and the crankshaft cavitates it and the whole thing melts down. The water temp appears to be ok but the block itself overheats.

Correct, most racers learn that the hard way. Always monitor oil temp as well as water temp. The Ford triton series of engines monitor cylinder head temp not water temp. The Ford Diesels compare oil and water temp to determine oil cooler efficiency.