Help! Running hot

If it also heats at speed that is a different issue. But my earlier post will cure that too.At speed , the fan is no longer the prime air mover. Air is being rammed through the rad by the vehicles forward motion. The shroud is also no longer required. Now you are looking at two or possibly three other things. Now you are again looking to see that the rad can actually shed the heat, and that the water is properly circulating.
That points to the #1) thing, the anti-cav plate and 2)the hoses,specifically the anti-collapse spring in the lower hose.
The third contributor here is the core-support seal to the hood. Without it air can be rammed over the top of the rad to enter the underhood area and make it difficult for the hot air coming through the rad, to leave. But I was never able to really prove that at 65 mph either.
A fourth contributor is if the carb is sucking hot underhood air. This is one of those ugly run-away theories. It goes like this; hot air coming through the rad enters the carb, and the heat gets transferred to the A?f as well as the intake, and the head etc. The hotter theair gets coming out of the rad, the hotter the air goes into the carb, and the cycle grows and grows. Along the way the heated air loses density and the carb goes lean,and the engine runs hotter cuz of that too. And again the hotter the air, the leaner the mix. Now along comes MR Sparky and and tries to light off this lean mixture , but he got to the party late cuz this leaner mixture wants to be lit off earlier. So now with the late start. the fuel may not have finished burning by the time the exhaust valve opens so it continues to burn in the manifolds or headers. Well that just drives the underhood temperature up. So pretty soon you have this little run-away nuclear reactor going on under the hood. Anyway, that is the theory.
A fifth contributor here might be late timing, but I have never been able to prove that one way or another. I have a dash-mounted, dial-back timing device, that can alter the timing from the drivers seat. It has a range of 15 degrees. It makes absolutely no difference to my running temp at speed with the timing jacked any which way, within the limits of the tool.

I can tell you that getting fresh cold air into my carb cured a lot of ails. But I am running aluminum heads. a minimum water temp of 205*, and TTIs. These guys put a lot of hot air under the hood. An awful lot!
But again, the primary thing at speed is to be sure the rad is seeing plenty of cold air ramming through it, and plenty of water circulating through it. BTW the flex fan turns into a wall when the blades flex to flat,heehee