For any radiator system there is an optimal time that is required for the coolant to give up its heat to the tubes and then the fins so it can be wasted off with the passing air. If the radiator will not conduct the heat as fast as the water is moving through you are operating beyond the radiators
limits and the heat will continue to build to a point.
Now if the heat build up cant be wasted off to atmosphere you are done.
Let say that normal flow through the radiator is 70 GPM and we suddenly try to flow 200 GPM the time it takes for the heat to transfer will not be sufficient and the coolant will pass right through without giving up the needed heat.
Increasing the size and heat dissipating capacity of the radiator will solve this issue.
This is why the two row radiator in a truck with a V6 will not cool a 454 monster.
The radiators capacity to reject heat is not there and I dont care how fast you try and pump the water through its not gonna do it.
More flow more core real simple