The problem many vapor systems had in the 70's was the flashing of the gasoline.

Controlling the mixture was too difficult with the tools of the day and if the gasoline flashed due to high temps it was like a bomb going off under your hood. A big bomb, too.

There was also no way to control the rapid increase in flow needed for acceleration. They were easy to flood out and then you stalled. And yes, there was a big problem with vapor lock due to the heat involved.

I knew a guy that fooled around with all of this back then. He was a pretty smart guy when it came to mechanical things but he never could get it to work as it should.