old muscle cars and summer heat...

[rebelrouser]

I think one issue is they are old cars, scale in the block is a problem, even if they are well kept. Most fuel now has alcohol in it, so a stock 70's carb will run lean compared to what it was calibrated for new, so that helps them run warmer. And the fuel evaporates easier, partly because of the alcohol content. One thing I do for my muscle car customers is block the heat riser passages, to help stop vapor locking. I have a buddy that like to drive in the county fair parade each year, and while the radiator would keep up, vapor lock was always an issue until we blocked the heat riser passages.