So I'm dropping the gas tank on my truck ('80 F-150, 300-6 engine, single 19 gal midship tank) yesterday, and I notice that the rubber fuel line leaving the tank is 1/4" diameter. I also know that the rubber fuel line in the engine compartment between the pump and the hard line is 5/16", as is the line from the pump to the carburetor.

Is it correct for the lines to be of different diameters? I'd expect the same size throughout the system. If this isn't correct, what size line should I have?

 

1/4'' at the tank, 1/4'' at the pump for me.

I had a piece of 3/8'' fuel line laying around that I replaced the metal line going to the carburetor with. It's a full 1/8'' too big, but it works just fine. Eventually I'm going to get a 1/4'' piece to go from the pump to the carburetor. Until then, it works.

I would think that the biggest thing though is that the fuel lines before the pump going to the tank should all stay the same size, that way the pressure "pulling" the fuel is somewhat equal.

 

Thanks for the input.

If 5/16" will fit snugly on both the outlet from the tank as well as the hard line to the front (and it should, I've had no issue with the 5/16" up front), then I'll probably standardize on that; I tend to agree with you that it should be the same size throughout, and I'd rather have it slightly too large than potentially too small.

If I were (a) smart and (b) not lazy, I'd measure the diameter of that hard line. Hmmm.