Power steering self centering adjustment

The Chrysler manual on page 19–20 describes under “test and adjustments“ a process to adjust the self-centering feature. My steering wheel wants to roll counterclockwise, the left. With the car running I tap on the head of back pressure valve body attaching screws.

I have tapped until I’m blue in the face and nothing changes. Note that I start with the steering wheel centered as I begin to tap and invariably it rolls over to the left.

I need some help before I take a hammer to the whole thing.