Not sure about your carb but most go leaner as the A/F screw goes in. Most vehicles also won't keep running with it bottomed out, at least at a low idle. Might actually be overrich. Is the booster dribbling at idle?
Yep, it's for fine tuning at idle. It's also usually happy at around 1 1/2 or so turns out on most older cars and yours seems to want to be seated to clean things up? That suggests to me that maybe you have a faulty power curcuit or too high a float level.
Not sure how your power circuit is configured but it shouldn't effect idle unless something is not working correctly. For example on a holley with a blown power valve, fuel can get throught the diaphragm and make it's way down the vacuum port. If the float level is too high, the added gravity will cause the A/F mixture to go slightly richer and if it is much higher, the fuel will drip out of the booster rather than a fine mist.
The Jalopy Journal
