Ok so here goes, I have a '78 power wagon with a mild 318 and I can not for the life of me figure out my problem. A few weeks ago it was running fine but while driving it, it would randomly start popping through the carb (rebuilt 600 holley) and i kid you not, it sounded like a 2 stroke going down the road. The popping was annoying and it had no power. Well it started getting worse and worse and the other day I got stranded. Motor would turn on (still popping) but it would not rev and would die in gear instantly. Anyway, I just put $300 in a brand new 600 holley and it is doing the same thing so I dont think its a carb problem. I checked for vacuum leaks multiple times and I have none. Anyway, I moved onto timing and I tried advancing it and retarding and messed with it for a good hour and got no where, there were no noticeable difference no matter which way I turned the distributer. I have full msd ignition and its all brand new. I know even new items can be faulty but I truly believe there is nothing wrong with my ignition system but I dont know at this point. I'm so frustrated with it and am lost. I have no clue what to do next.