.030" was the absolute minimum radial clearance measured at full gross valve lift.I left the .023" valve lash as a cushion. With this I would have a few thousands more radial clearance. Top ring land is .250" down on the piston,and the piston is .020"in the hole.Not a lot of options here as the closest point of contact is not at the very top of the bore but near top ring territory making a die grinder taper not very effective at the point needed the most.