With a 1&1/4" socket/breaker bar slowly bump/hand turn the crank so the timing mark slit on the dampener is coming up to the TDC (zero) mark on the timing tab & stop when the points "just" open (use your test light) & note the dampener reading at that point. EDIT Say your initial was "15" so that is what you would get (or very close to 15) if no damage (that'd be your normal timing). If it has jumped a tooth you will be way off from 15. You could divide the # of teeth on the crank sprocket into 360 to get the # of crank degrees it would off from 15 if it has jumped a tooth (& the wear as mentioned would exacerbate that # even further). Holler how it turns out.