Help with Flathead vapor lock

[Phil Waterman]

Vapor lock or flooding take your choice, but electric fuel pump with an isolation switch is the answer. Hot Rod Lincolns and Fords have run in my family as long as I can remember. I suspect that at times what is blamed as vapor lock is actually a combination of boiling the fuel in the fuel line and flooding the engine because the fuel boiling pushes excess fuel from the carburetor into the engine as soon as you shut of the engine. My first car was a 49 Lincoln which had been extensively modified, it had been by dad’s, it didn’t like the hot southern weather and the fix had been to replace the mechanical fuel pump with a electric fuel pump mounted back at the tank. It also had an under dash switch to turn off the fuel pump (early antitheft device). I leaner early on that to start that 350 cubic inch high compression flathead V8 on a 6 volt battery you did want to crank it over for long. So starting procedure was to turn on the fuel switch and ignition wait for the pump to stop clicking, meaning fuel line and carburetor were full of fuel, then hit the starter button. Usually the reward was the nice rumble of the dual exhaust. If however it didn’t start and it was hot out then you turned the fuel pump switch off pushed the gas peddle to the floor held it there and hit the starter button again usually this resulted in the engine catching after a couple of turns.

When my brother started playing with flat head Ford V8s he found that they really did like to vapor lock or boil the fuel line he tried the same fix but didn’t completely cure the problem so he added a return line to fuel tank using small tubing. In this way the electric fuel pump back at the tank could purge the line of any vaporized gas in the fuel line.

There even use to be a little after market fuel pressure regulator and return line connection that went just before the inlet to the Stromberg Carbs it allowed you to run a higher pressure fuel pump with out flooding the engine particularly useful when fitting multiple carbs.