Was the engine well cooled down last night when you got it to start again? I would think if the MSD box was bad you would have no spark. The small hiccup and the loud pow would sound like the engine stopped for a second and the pow was most llikely unburned fuel that ignited in the hot exhaust tubes. Also can you bypass your MSD and just run off a coil and the distributor? You could have a connector somewhere in there that has gotten loose and the heat is causing problems. If you think it is heat related get a bag of ice and put it on the carb and any other component that you want to cool down and wait a few seconds and try it and see if you notice any difference.
Ron
