Earl, gto guy has it right, let's build on his discussion.
There are as you know 3 parts of timing.
Base, you set by hand, 2 Centrifigal which is the springs and weights and solely dependent on RPM's
And vacumn advance.....which depends on throttle demand i.e., vacumn.
So figure what you have. Set the base, disconnect the vac can and plug to engine. Put a hand vacumn pump on the dizzy, watch the timing light and see how far the vacumn will advance the timing..if it stalls you may have to increase RPM's just to see the vac total....record the highest timing...
Now engine off remove dist cap take one spring off one weight, don't lose it. Leave vac can vacumn disconnected and plugged. Now with base at 8 or ten and timing light hooked up....run up the RPM's until timing will advance no more.
Record that number
Now you have all three critical numbers, base, vac and Centrifigal.
Base and Centrifigal should be 36 BTDC maybe 34 per 38. This is critical.
Vacumn must then be adjusted to give the difference to 52 ideally.
Use the adjustable vac can to adjust (and remmeber to adjust to crank RPM and not Dizzy RPM's....)
This test will show you what you have and what is working.....start there and adjust...10 base, 16 vac, 26 Centrifigal ......36 total (base & Cent) 16 more crank will give you 52 at light throttle cruise....is great but it can vary a little but the 36 to 38 total is most critical...