so this past weekend on my 73 mustang grande with 351C,  edelbrock  dual plenum maifold and edelbrock performer  carb - anyway, i had time to do the points conversion to the accel elec ign. Ended up running about 50% Smoother than before (was stumbling a lot at idle and figured the elec ign would help) and driving it for the past few days i had a much better idle which is a step in the right direction - Now today seconds after i started it it Backfired through the carb and stalled - when i started it again it was idling/running horrible, really rough - spent all day going through timing, checking plugs, wires, went through all the vacuum lines, checked fuel pressure, went through several carb adjustments, took off the carb, cleaned it and remounted it but this time using gasket sealer (just in case of a vacuum leak) since every stumble the vacuum goes with it. end result... nothing i did helped or pinpointed the problem - i do remember a few of times in the recent past the carb backfiring right at start up but engine idle had not changed and i just figured it was a timing issue since i was still trying to get it right - but today something is wrong but what - any tips cause i am stumped right now...

Thank's  

So, do you have all the settings at the factory reconmmended places, timing idle speed and choke?  Also did you make sure that the carb accel pump is actually working? or conversely working too good?
Stumble off of idle is usually, accel pump, ignition break down or vacumn leaks.  

Tough one Johnny,,,, When I first read it I thought you had blown a power valve when it backfired, then I realized that Performers do not have power valves. Engines backfire for a nummber of reasons, when they do it cold its usually a choke pulldown problem,,essentially the engine gets too big a dose of cold air and quits. When they do it warm its usually a timing problem, but you say you have checked and double checked the timing and the wiring and presumably the firing order. Does it idle bad when its hot? Does it run normally at other speed? Have you checked not only the timing but the advance? Does the pertronics have the correct gap ? Trying to help ya troubleshoot here.  

been working a lot these past few days and have not had any time to tinker with it again - i did however notice a faint almost like a clicking sound from the engine - not a valve tick but something else - so tues /wed i am gonna recheck / re-do all the common and usual potential causes, give it a fresh tune up and give a quick look under the valve covers, also considering a new carb that way i will be sure - give an update in a few days - oh, and since that incident it runs poorly whether hot or cold, idle or speeding