Nothing has been touched. Understood...... But something is broken! Some of us think it is the timing system, not the Dizzy. The place to "start" is to check the timing. In other words, check to see if when number 1 cylinder is a TDC, Top Dead Center on the compression stroke, that the timing mark/ball is in the proper position and the distributor rotor is pointing at No. 1 tower. If all that looks correct, then maybe it is an electrical problem and not a timing (mechanical) problem. It's the "backfire" part of your description that indicates out of time. If you said "no spark, no fire" then it would be the HEI coil or pickup or wiring or..... You don't have to "touch" anything for engines to have problems from wear and tear and age and so on. The sooner you start the diagnosis, the sooner you will fix it or advise your findings here for more suggestions. We can suggest and guess all day long. You have provided a very small amount of info to work with so far. We will be patient and wait. It's not a good idea to keep cranking in case something is bad wrong and damage may occur, but is it coughing still, trying to start? One backfire and that was it? popping thru carb while cranking lately? Be careful of fire also.
