I built a 440 with Sidewinder Heads and some aftermarket roller rockers. The valve geometry was off way-more than I was comfortable with. Two things in particular bothered me. 1) The sweep of the roller rocker on the valve stem wasn't centered which can cause premature valve guide wear. 2 ) The angle of the adjuster and the push rod when the valve was closed was HORRIBLE. A custom shim / relocation kit from B3 racing was required and completely solved my issues. This shim / relocation kit IS much more aggressive than the thin little shim the TS is showing in his original question, but to the point, YES shims can change the geometry and sweep of the rocker on the valve stem tip. Thin shims are most likely going to be used for minor corrections. My corrections were not minor.


First two photos are BEFORE photos.





Here's what the the corrected geometry with the B3 shim / relocation kit.