This is an adjustment tool for adjusting the APT [ adjustable part throttle] screw on the 1975 and newer Quadrajet carburetors. These are not to adjust the mixture screws with.

The Quadrajets come with a pressed in plug on top so if yours has not been removed and replaced with a screw in plug you will need to pull the top of the carburetor off to adjust the APT. We also have listings for a pair of these as well as a tap and plug kit plus all metal APT tools. Once the plug conversion is done this tool is also long enough to make adjustments through that top hole.