I have a 67 250HP 326 in my 65 Pontiac. Engine is stock except for Edelbrock Performer cam. My heat problem is opposite of most. I can drive around town, or idle ALL DAY and never go over 195 degrees(w/180 thermostat). When I hit the highway it slowly creeps up to 220-230. If I exit and start driving street again or even just pull off and let it idle, temps drop back down to mid 190's within 5 minutes. Never overheats on street, only at highway speed. I observed flow with cap off and it moves well when t-stat opens, no boiling over or spillage. I'm running 50/50 although I'm in So. Cal and don't need any freeze. I have a flex fan and factory shroud in place. I've used Wetter in my other Pontiac but never in this one. Since the problem is specific to highway, I don't think chemicals are the issue, but if I knew the answer I wouldn't be asking you guys. Any help appreciated! Ya'll haven't let me down yet!
Brian
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