A rotor stack for a gas turbine engine, comprising: a first rotor disk with a first rotor spacer arm , the first rotor spacer arm having a first flange with an outboard flange surface and an inboard flange surface , a first hole along an axis (T) through the first flange , and the first hole comprises a first counterbore in the outboard flange surface ; a second rotor disk with a multiple of integrally mounted blades and with a web having a second hole along the axis (T); a third rotor disk with a third rotor spacer arm , the third rotor spacer arm having a third flange with an outboard flange surface and an inboard flange surface , a third hole along the axis (T) through the third flange , and a third counterbore in the third hole in the inboard flange surface ; a bushing with a tubular body and a flange that extends therefrom, the tubular body comprising at least one axial groove along an outer diameter thereof, the bushing extending through the first hole , the second hole , and partially into the third counterbore in the inboard flange surface of the third flange ; a fastener that extends through the bushing along the axis (T); a nut threaded to the fastener to sandwich the web between the first flange and the third flange ; a cold-side groove from an outboard plenum along the inboard flange surface of the first flange to the first counterbore ; a hot-side groove along the inboard flange surface of the third flange to the third counterbore ; and an output groove along the inboard flange surface of the third flange from the third counterbore to an inner plenum , wherein the rotor stack is configured to permit a desired mixture of airflow from the outboard plenum forward of the blades , via the cold-side groove and along the outer surface of the bushing , and airflow from a plenum aft of the blades , via the hot-side groove to the outer surface of the bushing , into the inner plenum , from the outer surface of the bushing via the output groove . a first rotor disk with a first rotor spacer arm , the first rotor spacer arm having a first flange with an outboard flange surface and an inboard flange surface , a first hole along an axis (T) through the first flange , and the first hole comprises a first counterbore in the outboard flange surface ; a second rotor disk with a multiple of integrally mounted blades and with a web having a second hole along the axis (T); a third rotor disk with a third rotor spacer arm , the third rotor spacer arm having a third flange with an outboard flange surface and an inboard flange surface , a third hole along the axis (T) through the third flange , and a third counterbore in the third hole in the inboard flange surface ; a bushing with a tubular body and a flange that extends therefrom, the tubular body comprising at least one axial groove along an outer diameter thereof, the bushing extending through the first hole , the second hole , and partially into the third counterbore in the inboard flange surface of the third flange ; a fastener that extends through the bushing along the axis (T); a nut threaded to the fastener to sandwich the web between the first flange and the third flange ; a cold-side groove from an outboard plenum along the inboard flange surface of the first flange to the first counterbore ; a hot-side groove along the inboard flange surface of the third flange to the third counterbore ; and an output groove along the inboard flange surface of the third flange from the third counterbore to an inner plenum , wherein the rotor stack is configured to permit a desired mixture of airflow from the outboard plenum forward of the blades , via the cold-side groove and along the outer surface of the bushing , and airflow from a plenum aft of the blades , via the hot-side groove to the outer surface of the bushing , into the inner plenum , from the outer surface of the bushing via the output groove . <EOS>