Like a bomb went off under the hood...

I think I got mine to heat up because the system was borderline adequate, based on multiple factors... The air is not only less dense here at high altitude but also very dry which doesn't hold as much heat and in the summer temps can get well over 100*F. My 360 also had 10.5:1 compression and a too-small cam which made the cylinder pressures high and I struggled with constant detonation issues in hot weather until one of the piston ring lands finally gave up the ghost. I was running the factory HD radiator (my Duster was originally a 318 car with A/C) but have since scrapped it and now plan to get a nice aluminum one from ECP with dual extra-fat cores.