I don’t know about the timing, and cam but it doesn’t seem like it should run hotter while moving and bringing in fresh air. I had a 40 Chevy coupe 350 dual quads, mild cam just the opposite, idle in traffic it would over heat. I would have to pull off the to the side of the road let it cool down, run it 70 or 80 it was fine but when traffic would slow it would over heat. I had a new 4 row radiator installed and a heat shield, I think it was my engine was sitting too low and the air was going across to much of the top part of the engine the reason I say this is I also had a 41 Chevy 350 the engine set higher and it ran according to the thermostat. Just a thought maybe your gage is off!!!

Someone should be able to help. Where is Denny, he could tell you?

Richard