Adj vac advance on factory dist.
If I recall, the advance adjustment was mentioned on factory service manuals were high altitude tuning was the topic.
Believe not. That screw in the vacuum advance was not meant for field-adjustments; it's not like the idle mixture and speed screws on the carburetor.
The FSMs I've always read say this, and only this, on the subject:
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Vacuum Advance Curve
If only the vacuum advance curve is to be checked, connect tester vacuum pump hose to distributor vacuum advance unit and perform operations 1 through 3
under "Centrifugal Advance Curve", then proceed as follows:
(1) Turn tester vacuum pump "ON". Adjust vacuum pump regulator to vacuum test specifications. See "Specifications" and observe arrow flashes on tester degree ring to determine degrees of advance.
(2) If vacuum advance is below or above specifications, replace the vacuum advance unit. Retest vacuum advance curve.
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It's possible my memory's faulty and my spot-checks missed a year where the vacuum advance adjustment was mentioned, but I think probably not.