SBM Distributor overhaul DIY?

gzig5 said
Should the vacuum advance canister hold a vacuum when I pump it down with the hand pump? Seems to me like it should, but mine doesn't. It starts to move when I get to about 5 lbs but I have to pump like crazy to keep it from going back to the relaxed position.

Should hold better than that.
If/when you're going to use vac advance, I made a 'how to adjust' that's now in the "how to" archives.

gzig5 said
I've got the three spring kit from FBO so I don't think I should need to turn the eccentric, but I have a gauge I may be able to compare the springs with.

if you can compare springs with measurements, thats good.
Keep in mind length when its engaged will alter the tension.
I think just shortening the slots should help, but maybe not with the FBO plate. If the plate only limits the advance at high rpm, then you'll have to play with the springs and tension.

Shortening the inside of the slots, automatically puts more tension on the primary spring.

If the only option is limiting the advance,then its a bit more complicated.
With the stock springs the curve will look like this. Arrow represents rotating the distributor to move the whole curve up and get the 15* initial.

So then need to use higher rate springs to get the curve.

That will require some experimentation.