I'm not sure what he's thinking. I ran premium in my 427 this summer, drove it on some really hot days too and had no issues. New tight engine, just a stock size radiator, 2 row aluminum.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I run a stock (as far as I know never touched) 283 in my Beaumont with, as far as I know, the original rad. I put at least 5000 highway kms in a year and run premium. It runs nice and cool according to the aftermarket temp gauge unless I'm really pushing it on a hot day, I do have to top up the rad every once in the while. In other other words just as you'd expect for a 55 year old car.
No worries. The only reason I run premium is that I just don't trust the alcohol in my carb, especially if I let it sit for a while.
