Does this sound like vapor lock?

[JMD]

I have a mild build 454 in my ‘68 k10 that’s fed by a mechanical pump and an edelbrock 800 cfm carb. I also have the original style in-cab fuel tank with a new sending unit/pickup tube. There are two fuel filters in the system, one before and one often the pump and both are clean. The floats are set correctly, and I can’t find any debris in the float bowls.

The truck starts, idles, and drives perfectly. Temp gauge stays right around 200*. However, if I turn the engine off for a few minutes and then try to drive again it falls on its face at anything above 1/2 throttle. Acts like it’s starving for fuel. If I continue to drive it for a few minutes it will clear itself up and won’t have an issue until I shut it down again.

My theory is that while the engine is off and no fuel is flowing, the fuel is boiling between the tank and the pump (the fuel line runs on the inside of the frame and at one point comes within 6” of the passenger side collector). Once the truck runs for a few minutes, the flow of cooler fuel from the tank prevents this from happening and the truck runs fine again.

So do these symptoms point to vapor lock? Or should I be chasing a different problem?