Classic/Antique Car Repair: Vapor Locking 1949 Cadillac, modern cars, excess fuel

Question
I noticed you answer on vapor locking and was impressed.  I have a stock 1949 Cadillac with an electric pump already installed to correct vapor locking.  It has helped significantly, but I still have occasional hesitation at high speeds when the weather is hot 85-90 degrees plus.  When I actuate the electric pump the problem dissappears. I have a rebuilt fuel pump and there are no leaks in the system when I pressurize with the electric fuel pump located right off the tank. The glass filter bowl at the carb inlet has been added.  Any thoughts?  

Answer
I probably can't add anything to what I've already said on the subject. Somewhere, your fuel is getting heated to the point that it is boiling, or else air is getting into the lines somewhere - this is very frustrating, and I've noticed the modern gas is much more likely to boil with the new compounding forced on us by the smog rules.  Short of insulating the whole fuel line, I can't offer any wisdom on the problem. My 47 Packard will act exactly the same way on very hot days - over 100, and in severe conditions like mountain driving or parades - I just flip on the electric pump be glad I have it!

Modern cars all have pressurized fuel lines, with excess fuel and vapor return lines, so that fuel is continually circulating, mixing hot fuel with the cooler fuel in the tank - so the combination of fuel under much higher pressure (typically 60 to 80 Psi in a modern car) and circulation cooling makes modern cars immune to the problem - thus the refiners never hear a complaint about the vapor pressure of their product.  We're stuck!

Dick