just installed a performer manifold and edelbrock 1411 (750cfm)carb. I have my base timing set about 15* and with the vacuum advance its between 36*-38*. Well heres the problem from a idle to mashing the throttle it has a stumble or hicup. overall light throttle pulls are excellent with no detonation. also WOT pulls from about 1500rpms are good too! ive played with the springs and metering rods a little bit. but that doesn't really seem to help. Pulled a plug, light brown in color. So im leaning towards the shooter nozzle for the acc. pump, or too much timing advance? please help me out guys!

390 pertronix ignitor dizzy, flame thrower coil, .37 plug gap

 

Back off your base timing to 12*, leave your vacuum advance disconnected, see how much centrifugal advance you have, and at what RPM it's all in.

BTT