210 then levels off? 220 then levels off? These are not an overheat situation. Normal. These cars came stock with 190 t-stat, so Pontiac didn't even expect them to start cooling themselves off until just BARELY cracking the t-stat at 190 degrees. And a good 190 t-stat will crack open at 187 to 193, and will not fully open until 222 degrees (incidentally this is a direct quote taken from page 6A-3 of the 1968 Pontiac service manual).
So 222 degrees is how hot coolant needs to reach in order to allow full flow and max engine cooling. Pontiac expects this and the engines are designed to take it, plus several more degrees, with no problem.
Pontiac designed these engines to run all day long cycling back and forth anywhere between 190 and maybe 220/225 coolant temp. Why people seem to want to keep driving this number range lower has always confused me...
But if you're seeing it continue to rise to 230, 240 or higher? Yes indeed you have a problem.
If so, clear photos of your current shroud and fan setup might help a bunch.
Did you set tight clearance between your water pump vanes and divider plate?
What year is this car? 8 bolt or 11 bolt water pump?
If it maintains 180 while driving then that tells me water pump and radiator are probably fine. So I'd bet dollars to donuts you have nothing but a fan/shroud issue, or if your temps are never exceeding 225, you don't even have a problem at all and it's working exactly as designed...
