So decided I would "tune" my 40....got a variable advance timing light, found TDC line, painted it and started it to check timing. I set 7 degrees and the line was no where in sight. So I kept dialing it up and when I got to 15 the line was perfectly centered on pointer. Runs & idles OK with just a little pop every now and then in idle. I know, I know don't F with it if it's running OK, if it ain't broke don't fix it, whatever. The question is why does it run, accelerate fine with 15 degrees advance when the spec is 7. Don't really plan on messing with it unless there is some reason I need to. BTW no "ping" on hard acceleration in 4th gear that I can discern. Checked valve lash...seems OK. Haven't messed with carb, although I did notice idle mixture screw cover had been drilled out at some point....although I owned it for 33 years. Just curious...thanks.