Sorry this theory about "water going too fast" or "too slow" through the rad is bullshit.
If it was going too slow, it was a bad water pump, restriction, or slipping belt.
you can't drive it too fast so far as the rad itself, although a rad company (DO NOT ask me which) posted up they claim that too much pump can cause sort of turbulance in the block which degrades heat exchange. This gets to the old tale about needing a restrictor.
I will tell you THIS. OldManMopar posted that he thinks that some old rads can crack the tubes loose from the fins for various reasons. That seems to be EXACTLY what happened to my original 67 rad.
I have no idea what "they" did with modern rads, but the last gas 3/4T 5.9 V8, the old Dakota 5.2 I still have, and the 01 Diesel I still have---ALL are/ were run with NO pressure in the rad because the heater cores all leaked. They work just fine. NObody was more amazed than I
