Vapor lock or not, here is my story.
Yesterday here in Saskatoon, Saskatchewan it was 33 degrees Celsius (about 92 F).
I was driving to a car rally at the local Hot Rod club about 5 pm.
My 1950 Special Deluxe has an added electric pump inline with the rebuilt mechanical pump.
I have a heat shield installed.
The electric pump is wired to a push button, I normally only use it to prime the engine after it has been sitting for a while.
I drove about 15 minutes on the freeway and then turned off the freeway into the Industrial area where they are located. After about 5 minutes of reduced speed the car started to sputter and then die like it ran out of gas. I was pretty sure I was not out of gas but added 1 gallon from the jerry can I carry.
It would start and then sputter and die, the heat gauge was normal as were all the other gauges before it died.
I tried to start it with the electric pump energized and it would run longer and then quit.
I took a gallon jug of water that I also carry and dumped it on the carb as I have seen discussed on here.
Tried to start it with only the mechanical pump and it fired right up and I continued on the the rally.
Sorry for the long winded story, but I tried to include as much information as I could.