1974 Slant 6 backfiring through carb.?

Everything looked good on the timing line-up but it didn't change a thing with how it was acting. I figured what the hell and pulled the wires off the cap on at a time and moved them all clockwise one space. Tried to start it and it wouldn't start but didn't backfire so I did it one more time and she fired up and didn't sound to bad. I through a timing light on it and adjusted it a little and she runs better than before. The question still remains as to why it obviously jumped timing in the middle of the night or who the hell was under my hood.