Our 425 magnum started backfiring thruogh the carb about a month after tranny rebuild. Checke air boots, found a leak by engine intake, repaired. Hard restart. The only way we could get to idle was to take the vacuum hose off and then it would idle good not the best. Took carb out cleaned, new main jet, new diaphram, new midrange needle. Continued same problems. Changed E Clip to leanest setting, adjusted the choke. Idles like a kitten now. Continues backfiring starting at about a quarter throttle. It has had a gas smell and hard on gas(rich) since we got it used. Thinking it is an air flow problem and not a gas problem as air boots came off when we took the tranny out. Any suggestions? Maybe double check the intake boot? Exhuast does leak, but it has for alot longer than we've had problems. By eye the cam looks ok, ETC wouldn't cause backfire at midrange?
Thanks, weve learned a lot from this site, but quite haven't got enough knowledge to solve our problem.