My 76 308 failed the California smog test so I'm doing a small tune-up: new plugs, new plug wires, adjusting the carbs and setting the ignition timing. Having difficulty getting the timing set. The car is backfiring a bit through the carbs and idling rough. And I'm convinced it is the dwell on the points because it was running better than this before I readjusted the points (single points). In the process I discovered a great diagnostic tool: The Timing Light! In addition to using the light to set the ignition timing, it can be used to test the operation of the whole ignition system, i.e., is there spark at each cylinder and is it intermittent or not. Simply attach the inductive pickup to each of the spark plug wires, pull the trigger and watch the light flash. If it flashes regularly at all 8 cylinders then the critical elements (points, rotor, distributor cap, coil and wires) are likely working okay. On my car, on bank 1-4 all cylinders flashed regularly (at 1000 rpm) exept #1, which was intermittent. So I figure maybe the dwell is off or I have a bad plug wire. Will know more later, still working on it. But I thought I would pass this little garage knowledge on before I forget it.