My experience is years ago I paid good money for a "super desert special deluxe lol" custom copper radiator from a big source like mentioned above and it sucked for cooling at idle. I replaced it with a cheap champion off ebay and changed nothing else, problem solved, we figured the water was spending too much time in the radiator. Now we have several cold case radiators with the 1.25 tubes and all have been stellar so far on the street, three are 500+hp stroker small blocks. I will also add we all run flowkooler water pumps, high flow t-stats and adequate fan setups whether electric or mechanical.
