Float adjustment

[roblenderman]

I have a Street avenger 770 on a 351W stroked to 392. The engine is new from Roush. I checked my float levels after having a hard time once the weather turned warm and they were so high fuel was coming up the air horn. I turned the adjusting nut clockwise to lower the float and fuel level. I started the engine and let it idle for five minutes before stopping and rechecking the level by removing the brass screw in the sight window. After a few turns the level was just below the threads and a slight rock of the car would cause some fuel to escape. After driving a few miles and everything running fine I gave it hard gas. It made a small backfire and ran horribly like it was running really rich. The same way it was running before any adjustments. I took it home and opended the sight window to have fuel pour out again. I tried to lower the float some more but it is all the way down. The adjusting nut will not turn the inner needle any further down. What could be the problem?