Your shafts need relocating terribly. Look at how that rocker to valve tip contact is almost on the edge. Shafts need to go up and away from the valves to correct that. That's gotta be hell on the valve guides and stems, not to mention probably trying to round the edge of the valve tips off.
I did shim them up. I can bet the valves I got were longer than stock because the shop had to shim the crap out of the 340 springs to get the specs right.