Abstract: The present invention provides apparatus and methods for balancing stacked components of rotating machinery, such as in a gas turbine engine. Unlike conventional processes and devices for balancing stacked components, the present invention may use a single non-parallel spacer for obtaining an acceptable and repeatable component group balance. The non-parallel spacer may be used to compensate for rotor bow and the associated imbalance of the rotor group. By indexing a spacer with non-parallel faces, situated terminally at the end of the stack adjacent to the nut, rotor balance can be achieved without disassembly of the rotor group and clocking of its individual components. A spacer may also be disposed at any one or more of the interfaces between various components in the stack.