I am using it because that is what my builder said I would need and also the the makers of the fuel pump I am buying from Robbmc also are telling me that I need a 1/2 line. I have been told that it would also run just fine if I wasnt going to be putting my foot into the accelerator pedal, but at the higher RPMs that is where it would be needed to keep the 800 cfm carb full of fuel. Thanks for the info about your lines, but are or were your lines the steel braided?