It isn't likely the bore has worn that much. It is possible the wrong pump is being used- Carter used 4 different accelerator pump diameters- 5/8" through 3/4" in 1/16" increments. And there are different lengths.
There's a chance it may be missing the spring that sits under the bottom "skirt" of the pump piston that holds the bottom edge out against the bore, if it is really close to fitting, but not quite. In this case, it would pump fuel, but just not well. And IIRC, not all pumps used that type spring.
Tip- Be sure the S-link to the pump is installed so that when viewed from the front, it looks like a correct "S", not a backwards "S".
Last edited by cobalt327; 07-26-2010 at 03:30 PM.