350 sbc running hot on highway
I have a 350 in a '32 Chevy sedan with a th-350 tran. behind it. 3:55 rearend. Runs 180-185 in town, stop and go w/o air on, runs 190 with air in same situation. Go out on the highway and after 15 or so miles at 60-65 mph, the engine temp starts to go up and seems to run about 225 or so. Gets hotter if a semi gets in front of me. I have a hayden elec. fan on it. Don't know what the cam is but the engine is a 1969 vintage with Edelbrock manifold and 500cfm carb on it. Stock distributor with pertronix flame thrower II conversion in it and high voltage coil. How can I tell if it's timing (too retarded), to lean, air flow, or radiator? This is a real stumper for me. Where to go from here as I've done all the basic testing. I did back the timing off a bit after it was running hot and causing ping when accelerating.