I did some work today.
The distributor in the car was pulled. The Mallory instructions show that the stock arrangement is one purple spring and one brown spring. This is supposed to give a 2 step advance curve. The 2 step curve is a result of one light spring that gives a fast initial curve followed by a stiffer spring that delays the curve rate, hence the TWO stage curve.
My 14 degrees of advance is too short to have a 2 stage. The distributor had 2 pink springs and bent tabs to stretch the spring tension. It obviously wasn't a proper curve though. It was modified in 2005 when I had the car tuned at a shop with a dyno.
I mapped the curve today with the #1 distributor in place. From a 1000 idle, it advances right off idle, gaining about 4 degrees every 250 rpms and fully advanced at just under 2000 rpms. Yeah...FULL advance before 2000 rpms!
I took my spare distributor, the one I'll call #2 and changed the springs. It also had 2 pink springs in it. I changed them to to 2 orange springs. I put #2 in the car and found that it starts advancing later. I didn't get to drive the car because I still have some 110 Sunoco in the tank to use up. I need to run 91 octane to test these changes so I know if they are effective.
Distributor #1 now has 2 brown springs in it. I figure to test both in the car to see if I notice any difference.
Sorry to sound pessimistic, but I am still doubtful that I'll see any improvement. Here is why:
With the advance set to STOP at 31 degrees, I can run it up to 3000, floor it and get pinging. To me, this means that since the spark is done advancing, there is NO MORE CURVE to be an issue. If my thinking is wrong, I would surely appreciate a better understanding of it.
It seems to me that moving the curve later would help. The brown and orange springs are heavier than the light ones the #1 distributor had, so maybe it might help a little.