Lotus did our cooling system specs sized to power out put paying attention to design & flow rate of the water pump. In our LT5's I think it was gallons per minute per 1000 rpms per 100 hp......or something like that. In the end the max flow from the pump ( past 5,400 rpms up to the limiter ) was way more than the stock C4 radiator could tolerate. GM was to have had another type of radiator designed & built. That never happened, instead they designed our thermostat housing & thermostat to serve a by-pass function when the flow from Lotus' water pump exceeded the radiator flow/pressure limits. Past a certain flow rate our coolant just makes a circle in & out of the block with out going thru the radiator. If it did we would blow up our OEM radiators, I guess the plastic side tanks would have been the first weak point, and then maybe the core? I know with some after market C4 radiators w/ welded metal side tanks, our water pumps with an incorrectly boxed T-stat ( wrong stat in right p/n box ) will explode the core of some of those aftermarket rads.
Tom