QUOTE(The Cabinetmaker @ Oct 6 2017, 08:39 AM)
It's been reported, and first hand experience agrees, they went to the two port pump and moved it to the from too escape the dreaded vapor lock. I moved the pump on my 73 to the front trunk for that very reason in 78. Pump never lock again after that. The pump was situated about an inch away and directly in the path of the dump from the heater valve
Yes, I've moved the pump to the trunk on all of my cars to avoid vapor lock. But, in that case I've been even more keen to have the pressure relief valve on the pump. Otherwise if the supply line, return line, or regulator, become plugged in the engine compartment, the fuel line(s) running through the tunnel become highly pressurized (50+psi). Not a good situation in my opinion. Especially if you still have the original plastic lines in there.
Maybe the newer 2-port pumps can't build that much pressure? The 3-ports will go beyond 50psi.