My 75 runs about 235 F when the ambiant is over 70 F and when I roll down the road over 2300 rpm (which is about 60mph with my 3 speed). The 160 degree t-stat I put in does not help it. I plan on putting in a 700R4 in it later, I'm sure that will help alot getting those RPM's down. I do plan on putting in a 350HP engine later so that would need cooling issues addressed sooner than later. Any thoughts? I am hearing that C3's run hot so what's the fix? Thanks, Justin

It could be the radiator. a good test for that is at slow speeds if the temp drops to normal levels but rises at higher speeds then I would suspect the radiator. Also check your timing. it may be too high

I have always thought that older Vettes ran super hot. I can remember cruising in my buddies 78 and my legs would be burning hot in the summer. Here are a few fixes for the problem and checks. Check your thermostat. Might want to go with a cooler one like a 160 degree one. Better fans will help out alot and a high flow radiator will do wonders. There is also a products called water wetters on the market that could help. I hear mixed reviews on them though.
Here are some:
http://store.summitracing.com/default.asp?target=egnsearch.asp&N=4294925094+4294920362+4294882688