I have a 1985 TPI 305 IROC, the thing is in slow city driving in the summer the temp stays 220-230 but when i get on the highway it gets up over 250, the fan is working fine and the coolant is at the right level any reason why it gets hotter in the highway???

 

Is your air dam intact? A bent or missing one would increase your highway temperatures

 

yeah i would check the air dam, its under car, under the radiator.

could also be the lower hose from the water pump to the radiator collapsing.

start off by checking those two items first.

 

Mine's doing the same thing. I have a new water pump, new hoses, new clamps, a new radiator, and no leaks. My air dam is intact but I'm wondering if it's developed flex and maybe doesn't hold it's ground at highway speeds. I was going to support it or maybe tilt it slightly up with some brackets or something.