I have a 360 magnum based 408 in my 1970 dart. I've been fighting it this summer trying to make it run cool. Its a .030 over with about 750 miles on the build. I have edelbrock heads running with a 234/238 @.050 hughes cam. Its calculated at 11.5:1 compression. I had a demon 750 carb on it and have swapped it out for a Holley Sniper EFI. Ceramic coated headers 2.5" exhaust. Timing is set at 16° base and 33° all in. I have a 727 with a 3200 stall. I have swapped out the water pump with a flowkooler high flow pump with no difference. I swapped from a 195 thermostat to a 180 with no difference. I had accidentally put a hole in the radiator while swapping fans and now have a champion 22" 3 row aluminum rad that made no difference. I had a 16" Spal Syclone fan on it and have recently swapped that out for a much better Chevy HHR fan/shroud that fit the 22" radiator perfect, that seems to have helped some. Im running the magnum serpentine drive and water pump so a mechanical fan/shroud is different than an LA. The HHR fan will suck a dollar bill to the grill, it moves a BUNCH of air. The car will idle at 185° no problem. After about 10 minutes of driving the temps start rising slowly and within 20-25 minutes ill be at 230°. If I park the car and let it idle, it will drop back to the 180's within a few minutes. The temps are verified with the Holley screen, factory gauge, aftermarket gauge and a temp gun. Im planning on trying to restrict the 1" bypass hose down to a 1/2" or 3/8" to force more water through the radiator and prevent some hot water from recirculating back to the engine. I dont know what else I'm overlooking.