Valve lash caps??

I used them in my junior dragster motor program. With lighter weight titanium valves I needed to bring back the circumference of the valve tip to match the lifter size. Otherwise the tip would beat a hole in the center of the lifter creating all kinds of clearance issues and disassemble problems. Most generally they can be used to fix slight geometry issues, are used with smaller diameter stem titanium valves and higher rev motors. Street motors with no exotic metals. Nah, save the trouble.