For that leak, Check the bowl screws to see if they're tight. That's the easiest thing to check.
To adjust floats, remove the inspection screws on bowls (on sides of bowls) and adjust the float screw and locknut adjuster on top of the bowl until fuel level is even with bottom of inspection hole and fuel just barely leaks out. Then secure the locknut without changing adjustment and replace the inspection screws.
Backfires may have damaged the power valve. If so, the front bowl and metering plate needs to come off to check things. If valve is wet on both sides or will not hold pressure/vacuum it needs r&r. Plan on gaskets needing to be replaced then as well because they will tear if you haven't spent money buying spares. When you have spares, they usually come off just fine....
A lean condition may be due to the adjustment of the accelerator pump actuating arm (screw and spring) the plastic cam on the throttle main shaft (different profiles are available) and/or the position of this plastic cam on the throttle shaft (position can be changed by the attaching screw)
The air adjustment screws (on each side of metering plate) may need adjustment. I usually GENTLY bottom each, then back out one half to one full turn each and proceed to adjust each the same amount until the best idle is achieved- highest vacuum, most consistent rpm, whatever. If an automatic car, I was taught to do this adjustment with the car in gear and someone behind the wheel with their foot on the brakes. Shorty said "you need your car to idle right when it's in gear and being driven, not while it's just a' idling while in park..." and that made sense to me.
Things like jets, filing or milling the metering plate(s) and body flat and more also need address. Some remanufactured carbs are not cleaned adequately, so that defeats other properly operating/adjusted items.
This should get you started. There are a lot more educated Holley people here who have actually read the book. Maybe they'll post some opinions.
1967 Galaxie 500 Red original Q code 428
1967 Galaxie 500 White with Black stripes 428PI clone- car is dead & long gone, sold near Oak Ridge TN 2000, would love to find it.....
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