The 1 1/2 turn initial setting is a beginning point to allow the engine to idle on startup after a rebuild. Use the vacuum gauge to fine tune the mixture, unless you're willing to invest a few thousand dollars in a 4-gas exhaust analyzer for a really high tech way to determine the ideal mixture setting.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!