I had battled a high coolant temp issue for a while (stock system with shroud). The temperature would slowly creep up to 220-230 no matter how the car was driven (highway, stop and go). Turned out rust/crud from the engine (which had been tanked when rebuilt) slowly clogged my new radiator. I had the radiator rodded out, put in a TEFBA filter to prevent the radiator from getting clogged again and the temps are normal now. I did see significant crud when the filter was first installed, and it is still trapping small crud particles. Just something to consider when all else fails.