Rough part throttle. Good idle and WOT

[Yowzah]

My previously sweet running 7041262 Pontiac 455 suddenly runs rough at part throttle, but perfect at idle and wide open. Specs- 455 Pontiac, Crower Ram IV hydraulic, 10:1 compression, ported 6X heads, aftermarket ram IV exhaust manifolds, TH400 2800 stall. 7041262 modified after reading Cliff's book and using recommended parts,  .054 idle down channel, .070 main air bleed, .050 air horn air bleeds, .030 pump discharge, .073 primaries, .043 primary rods, DA secondary rods, .250 float setting, factory power piston spring. Idles at 15 inches. 34 degrees total advance.

Problem came on progressively rather quickly. Took the carb apart twice now to check settings. Only thing I found was a fairly plugged fuel filter. Inside of carb was clean. Power piston feels smooth in the bore.

Feels lean to me. Very rough but gets slightly better with more throttle. WOT it screams and no bog going to WOT.

HELP!

[429bbf]

you don't think a little garbage got in the accelerator pump  discharge  holes .that would seem like the most obvious.you say it has no effect on idle or wot.just a thought

[Cliff Ruggles]

May have debris in the idle tubes, I'd start there.....Cliff

[Yowzah]

Cleaned and checked all specs. Put a new fuel pump on just for grins, even though the old one tested good. Still has a bad partial throttle miss. I then installed the carb on my 454 Chevy truck, and it ran flawlessly. I now suspect ignition. I have a factory point type distributor With a Pertronix conversion. I am going to try an HEI next. I am hopeful the Pertronix is the culprit. At least I know at this point it is not the carb. Whew.

[Yowzah]

 Fixed the problem! Turned out to be the Pertonix conversion in the distributor. Installed a HEI and cured the partial throttle misfire. Carburetor runs superb. Once again Screams like Chief Pontiac on the Warpath.