holley 750 carb hiccup?

hello all, odd one here, had like a miss, would clear on higher rpm but still not pull clean, it was like several leads were breaking down and coming in at the same time or you losing ign for a second then getting back but know not ign as not misfiring, i swapped the leads anyway wondering any suggestions on carb, its a freshly rebuilt holley 750 vac sec, igh is new msd streetfire,new elec dizzy and new coil, wiring is 100% as i rewired whole car, i have a soot deposit around top of carb / butterfly, hoping its not a valve blowing back but the carb popping back thro, cheers in advance, nathan.ooh, its a 440 manual.

I don't think it is easy to tell whether a miss is from ignition or fuel. If you install an O2 sensor, that will give more diagnostics. Next time you have the exhaust out, weld an O2 bung on to position yourself. I put 2 on my pipe for wideband and regular, that way I can calibrate the wideband.

hello, many thanks for that, im thinking of getting a x pipe fitted at some point just past my headers will fit one in there, its a real odd one espically the sooty carb.tis an odd one this

If it backfired through the carb, it probably killed the power valve which will cause the power valve not to function. Try changing the valve and see if it cures part, or all of your problem. From there, you might want to experiment with different value power valves.

a point in right direction! rayer: did the test, wound mixture screws in, didnt stall........ordering a kit that protects powervalve by releasing pressure caused by backfire then..................get car settup properly!