From the info in the Santucci book, they list 3 different gear pitches. The first is 20° which is on the first upgrade, 14° which is on the first adjustable and then 0° which of course is the straight cut iron gear. My engine builder said the straight cut would be the strongest.
Scott, who has made the sets that you've seen? Were those Jesel too or someone else? Do you think it would be feasible/possible to cut extra keyways in the adjustable sets for 2° advanced and retarded adjustments? I think what's in those now is just 4°.
