I have a Great dane Super Surfer, With a Kohler CV18S 61548 That was run with low oil. The employee didn't tighten the drain plug. I took the heads off and one of the pistons has an imprint from the valve in it. When I got the mower, The valve covers were off and this valve had the push rod and rocker removed. The pistons and cylinders look good, the cams are moving the lifters. I would like to replace the bad push rod and lifter, and rebuild or replace the head with the bad valve. There is 600 hours on the machine and therest ofthe engine looks great. Any input?