I have a 350 with the manual fuel pump and it has only two lines, one to the carb and one to the gas tank. The 305 in my car has two lines going to the gas tank and 1 to the carb. Why is there two going to the gas tank. The two going to the tank are differnet sizes, theres a big one and a small one. Can I plug the small one and just use the big one?

 

anyone know what the 3rd line is for?

 

return line for the fuel IIRC somethin for emissions or something like that im not sure i never use it

 

It's a return line. Plug it if your pump doesn't need it.

 

That line has nothing to do with emissions. (you may be thinking of the vapor line between the gas tank and the charcoal canister?) It's the excess fuel return line. On your 3 line pump, any excess pressure beyond your 6ish psi gets directed back to the tank. On the 2 line pump, the excess gas just kind of stays in the pump. Some people say that by keeping the fuel circulating, the 3 line has a lower chance of vapor lock.

Yes you could use your 2 line pump on the engine and cap off the second line on the car. But you might as well use the 3 line pump off your 305 and hook it up. Unless your 350 pump is an actual high performance aftermarket one, chances are they flow about the same.