Man I wish I knew what I was doing. I had one motor in my Bronco that I couldn't keep cool and now I'm working this one. I have several items checked off the list, but no flush. The radiator is brand new but probably small and lacking fans since it is not a high dollar one and I bought if from Speedway. I've filled and drained several times, tried different thermostats and caps, built cardboard setups to direct air only to the radiator, and no difference. It runs at 210. I haven't flushed it but it was a fresh rebuild that sat dry. I ran it without the cap and with the 180 thermostat turns on and off at idle and water flows. Is the flow rate right? Who knows. Is the water pump working right? I don't know how to tell except that it moves water and isn't leaking. The radiator spits water into the overflow and then settles in at the head space it likes I guess. The only next step I can think of without any real data is a higher capacity radiator with a couple heavy flow fans. If it doesn't run cool next Saturday, there will be no NORRA 500 this year and that would suck.