Overheating

[LIRacer]

My big block 1970 442 (I also have a 72 LT-1) runs hotter when I am at highway speeds. The temp gauge goes almost to the mid point when it should be in the first third. I am figuring the water pump or thermostat is at fault.

Need help on this.

Bruce

 

[Jack]

Bruce:
Verify the gage w/ a known stick t'meter. I doubt it's the pump. Much more likely culprit is t'stat. Another likely culprit is residue buildup in rad's core-flues. Prestone P/N AS100 Heavy Duty Cooling System Cleaner is the best ... but not so common on parts houses' shelves these days. GM dealer has it under GM P/N 12346500 ... about $6.
JACK:gap

 

[Bob Chadwick]

Check your air dam and seals. Highway spped problems suggests that the 60 mph air is not getting to where it needs to be.