I've been fiddling with the timing on a B20 with a Crane flasher in a Bosch 0 231-153-009 distributor (strictly centrifugal, no vacuum advance or retard). I haven't been able to find timing specs for this distributor in any of the Volvo literature, so I started out with +20° @ 800 RPM. That way the advance maxed out in the neighborhood of +45° at around 3200rpm. The car ran fine, no pinging, but I was told that this was way too much advance for good performance. So, I have been retarding the thing gradually, and every time I retard it further the engine seems to run better and rev freeër, and gas mileage improves. I'm now at +5° @ 800 rpm and the advance maxes out at about 30° @ 3200 rpm. Seems to run better than ever, but when I switch off the ignition after a good run, the engine runs on for a single "pop" -- not really dieseling, just one "pop". Is that a sign that I may have retarded the thing too much?
Bob S.