Advance question

[dadsgreentruck]

I've been trying to get my old 307 tuned and optimized as much as I can lately and I ran into something that is a little confusing.

I've got an old Mallory dual point distributor that I converted to electronic, so that's all good, but the advance has me a little puzzled. Mallory says the vacuum advance should start to come in at about 7". At idle (about 850 rpm) I've got 15-16". If I disconnect the vacuum line to the advance canister, the timing mark doesn't move.
Do I have a bad vacuum advance unit or do I need a different one for lower vacuum?

Also, at 850 rpm it appears that the mechanical advance is already coming in. Do I want to get a curve kit and put in some stiffer springs to move it up a bit?

Tim

[Sinister]

Are you hooked up to ported or manifold vacuum? The springs in the advance kits aren't that strong really. Might be better to grab some springs out of a distributor at a junk yard. Factory springs are usually stiffer then even the stiff springs in those kits.

[dadsgreentruck]

Oh yes. I forgot to mention. I'm running full manifold vacuum. Carter AFB, plugged into the port on the drivers side.

[Sinister]

Might want to test the vacuum advance. This is on an HEI, but should be similar on yours.

YouTube- HEI distributor vacuum canister test