Fuel Return Line - Do I Need One?

67Dart273 said

I'm a huge believe in return line systems. First one I ever saw / had was factory on my 70 RR 440 V code car. IT WORKED. Very little trouble with vapor lock

I added on to the Dart before converting to EFI

Don't confuse fuel return with the 70's evaporative control system (carbon can)

Click to expand...

This.

And as RRR pointed out, the fuel we get today is nothing like the fuel available when the car was built. Fuel today is formulated to work in EFI systems where it is pretty much impossible to vapor lock the supply line. Not true in a carb'd application, and the fuel formulation no longer allows for that.

Said differently, cars that wouldn't vapor lock on the fuel available when they were built very likely will vapor lock on today's fuel - even when everything is EXACTLY as it left the showroom floor.

I like mechanical pumps for their simplicity. If I could put a mechanical pump at the tank I would. I'm slowly converting my whole fleet to electric pumps with return systems. Keeping the fuel under pressure is the key to no vapor lock. Mech. pumps have a vacuum between they and the tank. Exactly what you don't want with modern fuel.