Help setting timing and vac advance

I don't understand any of what you said...but you're wrong.

That is not a reasonable approach to anything.

standup303 said

I adjust my distributor vac advance can till it’s pulling 10 inch (test it with a Mity Vac) and that’s it?

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I don't understand that. Might you mean it's adjusted such that the unit STARTS advancing at a measured 10" of vacuum?

The distributor vacuum advance can doesn't 'pull' inches of Hg. It pulls a rod WITH the application of vacuum to the can. It does advance the spark depending on the amount of vacuum it is attached to and when that advance starts in the vacuum 'curve' (given amount of vacuum at particular RPM) is dependent on the setting of the allen-spring INside the vacuum canister.

Yes, you can check all of that with a Mity Vac..or any vacuum source.