I am sure this question has been asked before, but what HP level is the stock stage1 fuel pump with stock fuel lines good to? I am running stage 2 alum. heads, 3" exh., SP1 intake, KB cam .540 lift @.050 and 1.6 ratio roller rockers. The engine seems pretty flat on top end - fuel starvation? With all the problems discussed with electric fuel pumps, I have been reluctant to make the change! Would just going to a bigger fuel line help and on a 70 GS is that a 5/16 or 3/8 line? Is that meaured on the ID or OD?
From what I've gathered, 500 hp is the most you can hope for with the mech pump. Your combo sounds like it is over that mark.
If you want to diagnose to know for sure, put a fuel pressure gauge on it and see what the pressure is at WOT under a load (top gear). If it falls to 0-3 psi, you need more pump.
Before I went to the stage2 heads, bigger cam and bigger gear and bigger carb I was getting about 3psi. I need to adapt a fuel gauge to this setup and see what it is now. I would assume it would be less than that now!
