First, check the steering gear to see if it's on the "center point" with the wheels straight ahead. There's an area of zero clearance right in the middle of the sector gear that needs to be adjusted for the proper preload as the gear passes through the center of its travel, and that point must correspond with the center of the wheel travel side to side. The steering gear preload is adjusted by disconnecting the drag link and turning the gear through its full travel, and adjusting the screw opposite the output shaft to get a 10 inch/pound rise in turning effort at the steering shaft center nut as the gear passes over center.
If the wheels are not pointing straight ahead at the center point of the gear, something about the drag link/tie rod relationship is worn or bent. On a stovebolt, there's no way to adjust the centering of the wheels without fabricating an adjustable drag link.
Jerry
