A body Power Steering "self turns"

Hello everyone , I recently installed a new power steering gear box in our 1966 Dart. I rebuilt steering column , drained and cleaned pump. When I started car I rotated steering all the way right to left at least 8 times. I held slightly at end of turn to put a bit of pressure on system to bleed. Turned off car. Restarted car and gearbox turns by itself to left. I rotated again thinking I did not cycle system to get all air out. Still when running gearbox turns wheels to the left. They will go all the way to stop. I am figuring a defective steering box but thought I would ask if anyone knows of an in-car adjustment that can be made. On some older model GM cars there is a 7/16 nut under a cover on gearbox you can access. You turn nut slightly either way to take the "self turning" out of box. Thought I would ask the best before I pull gearbox back off. Thanks all for your time and help. Ed