First time with the vacuum gauge (yeah, I know), and I've got some tuning questions:

My setup is a 413 RB, 10.1 to 1 compression, cam is a .480/.480 lift, 236 duration at .050, lobe center is 108*. Carb is a Speed Demon 750.

Timing is set at 38* total, all in at 3,000 RPM. Initial is 20*

Right now, my vacuum gauge reads 13 Hg at idle (1,100 RPM) in neutral. Dropping in to drive gets me about 6 Hg. In drive, its around 20 Hg.

I'm not too familiar with tuning using a gauge, so forgive the dumb questions - where would you go from here, or am I in the ballpark?

20" while driving? You're running pretty darned efficiently in my book, for your set-up!

Drive idle is pretty low, but that's probably your cam. If the needle is staying fairly stable at idle (cam considered) then you're OK!

The trick is to get the highest vacuum you can at idle, and to have the needle as stable as possible. The lumpier the engine, the less this applies, but try to get the most vacuum you can anyway.

I'm not sure I understand how dropping into D increases your vacuum. Shouldn't it be even lower than in idle especially since the rpms drop? Mine in idle (900) is around 18" and in D (650) around 14-16.

Timing seems ok. Think mine is now at 15* idle and 34 all mech in (my dist pulls around 20* vac as well so around 54 all in).

Now that you have it close in Neutral, put the tranny in D, apply the emergency brake, and reset your mixture screws again. The best vacuum in D with brake applied is what you are after with an auto trans. Your vacuum drop from N to D sounds like your idle circuit is a little lean but a problem that you might run into is that the Speed Demon does not have remoavable idle air bleeds.

Thanks. I should also clarify that my distro does not have a vacuum advance.