Radiator upgrade experiences?

Concentrating exclusively on the tube size or the number of cores is a mistake. Just adding larger tubes or more cores doesn’t make a radiator better in and of itself. All of those things play a part, tube size, number of cores, number of fins, overall size of the core, etc. At some point a giant tube loses efficiency because all the water in the tube isn’t in contact with the wall of the tube itself (think water in the middle of the tube). Just like more cores eventually becomes less efficient because of air restriction. Plus the overall thickness of the core limits fan size and options, which is just as important as the radiator construction.

Honestly most of the cooking problems people seem to have here are from pulley diameter mismatches and using the wrong water pump with the pulley diameter they’ve got. Remember there are two vane counts for the pumps depending on what the pulley configuration was. It’s a cooling system, a good radiator is only one part.