My car is a 68 retrofitted with triple su's and the rest of the mods to run like an s1. I have been happy with it since finishing a few years ago. Late last year I let it run dry and it is no longer a smooth runner. Under moderate to hard acceleration it bucks severely. During all the roughness, the tach remains steady and I have assumed the fuel system is at fault namely the pump, gas tank filter or fuel line filter. The bucking is severe enough that I do not believe an individual carb could cause it. At low revs operation remains smooth. So as a test I detached the fuel line where it connects to the carbs and connected it instead to a flexible hose. The hose rises 5 feet above the pump which should cause a 2 psi pressure drop. Then it empties into a large bottle. Fuel flow was slightly more than 1 l/m which should be enough I think to sustain 120 mph at 8 mpg. Any thought anyone? I will try new coil in case I am wrong assuming a fuel issue.

 

Hi Bill,
I think you are on the right track suspecting the fuel feed. I would look into the filters. Particularly the on on the tank.
Good luck and let us know how you resolve the issue.
Bill.