Distributor recurve
The tag number on the donor distributor is 3874876 and it was on a 2bbbl auto car. If I'm reading the chart right, it is only supposed to provide a maximum of about 7 degrees of mechanical advance at the crank (~4.7 at 2200 rpm compared to ~1.2 at 600 rpm, so 3.5 degrees difference at the distributor, times 2). I was seeing 7.7, consistent with the chart. Combined with the 12 degree initial setting, the total advance would be about 19 on the Super Six car from the factory. Does that seem right? I know my engine likes up to 20 degrees at idle, so I would have no problem bumping the total to about 28 with the distributor as is.
If I want to allow more centrifugal advance, I guess I will need a longer long-loop spring.