[jeepguy1948]

There was a long thread about this exact problem a couple weeks ago. Look it up and check it out. I wish that I could loan you one of the carbs I have rebuilt myself (and tested) then I would know that at least that wasn’t your problem. I suggest that you try a carb that has been put through its paces on another car. I had the problems you describe and it turned out to be both the carb (tried 3 supposedly rebuilt carbs and ended up making one good one with parts from all 3) and a bad coil as well. I know that you say you replaced the coil (had it actually been run on another car? I no longer trust anything “new” until I have tested it myself. Backfire is usually from running lean, but yet your plugs show rich. It is impossible to describe without showing you but I can tell you that without question setting the float level per the book that they are two high. I do agree with both post #2 and post #3 (I like Sea Foam better than MMO but that’s me. Backfire out carb would be an intake valve rather than an exhaust valve if a sticky valve is the problem. Hope this helps, check out that other thread. Good luck, these things can be a nightmare.