From your most recent pictures, I don't see how that one valve rocker would be contacting the valve cover unless the valve cover may be dented or a bit deformed in that spot???
Can you show us the wear spot on the inside of the valve cover???
The circled rocker arms "adjuster" is showing a significantly different setting compared to the other adjusters in the picture. Majority of the adjuster settings are showing about 3 to 4 exposed threads (not a spring) on the adjuster. The circled one is showing either none or barely 1 exposed thread, making that one valve adjustment much different than the others.
That may be because some one used a different length pushrod as a replacement for a bent/damaged one???
Only way to figure that out would be to remove that one and an adjacent pushrod and compare lengths.
Another step in the investigating process.
Dan
