Timing Curve

midnight340 said
Well, I'm sure the vacuum advance is not meaningful as there was no load on the engine.

Agree but you can make use of it. **

midnight340 said
Vacuum I've been watching. (Ran a hose to inside and have a large vacuum gauge hanging on the mirror.) So far it does seem like the vacuum is creeping a bit higher as I get things tweaked better. Does that make sense?

Yes.

midnight340 said
This cam is 235/243 at .050, more than I've had before, but torque is good, and the power brakes have worked great.

I'm impressed too. Mine is around 11"Hg at idle (N) with 230 @ 50. I'm sure this is due to the tighter LSA shifting the intake closing and maybe a little bit to do with the lobes Hughes used at the time.

** If you have the vacuum for each of those measurements timing with vacuum advance, then subtract mechanical from the timing measured. That will reveal the vacuum advance contribution..

Using your first graph:
900 rpm, 33 - 18 = 15* at what vacuum ?
1250 rpm, 40 - 18 = 22* at what vacuum ?
and so forth.

You already know that the engine crusing vacuum is around 17"Hg. With the vacuum advance graphed then the amount of timing added during cruise will be known.