I've been trying to recreate the curve for the distributor I had on my '73 1300 beetle, and I am looking for confirmation that I'm doing this correctly, especially the vacuum advance. According to my calculations:
mechanical advance
0 deg @ 1120 rpm
9 deg @ 1500 rpm
22.5 deg @ 3700 rpm
vacuum advance
0 deg @ 80 mm Hg = 10 kpa … 90 kpa
10 deg @ 26.5 kpa ... 73,5 kpa
10 deg @ 40 kpa ... 60 kpa
Now, the original distributor should be timed at 7.5BTDC, so I have added 7.5 degrees to the mechanical advance figures above. Does it all make sense? I think I am getting too much total advance when revving high (34-35 deg).