I followed Mac’s advice (“check timing 7 ways from Sunday”) to a solution. Actually it took two Sundays because the centrifugal advance of the Pertronix Flamethrower was so different from the 45DE4 that I replaced that I did not trust my measurements. The short version is that the Pertronix has much more centrifugal advance increase below 1000 RPM than the 45DE4. It is 15 degrees in 500 RPM rather than 8 to 9 degrees in 1000 RPM. Above 1000 RPM the two are "kind of" the same. When I changed the distributor I had dialed in the previous advance value at idle (650 at the coil). This resulted in way too much advance above 1000 RPM. On realizing this I dialed in the desired advance at 1500 RPM and now have my old car back. I do not know why too much advance caused the engine to act as it did. I thought too much advance would cause it to ping. In any case it is nice to be able to comfortable drive the car again.
BobK