I would not use the diesel flush method to clean it when running. I did this once on an old Cadillac V8 with disasterous results. Spun a rod bearing, ruined the crank. Also be wary of replacing the lifter that has work hardened and "worn in" to that cam lobe. I would start by adjusting the lifter by the book and failing that removing the lifter, disassembling it and cleaning it in whatever your rubber gloves can stand up to. Look for a collapsed or broken spring under the check ball, a pitted check ball or seat. You can replace the internal parts of the lifter except the inner piston which is likely a lap fit to the bore. I would avoid replacing the lifter body if possible.
If you must replace the lifter body make sure that it is the proper material (chilled iron, steel, etc.) Then make sure weather the cam is ground flat or tapered. If it is tapered make sure the lifter it is ground to a crown shape and is not flat. If they are flat and the cam is tapered, they will gall one side of the lobe and/or the edge of the lifter, making short work of the cam. Many cams are ground to a 1 or possibly 2 degree offset from square with the line of the cam bearings. The object is to make the lifters rotate, reducing wear.
On a past job, I was able to grind a 1 degree crown on flat lifters that had been on another cam, which had been ground flat for reasons I no longer remember. I used a fine paper on a bench-mounted belt/disc sander with the table set to 1 degree. I checked them with a machinists square and magnifying glass under a bright light. I used cam-assembly lube and observed break-in procedures. The cam has been in the engine about 10 years and about 100,000 miles. If you are careful you can successfully do a lot of hand fitting.
I someone knows of specific years/cams that are ground flat, please weigh in here.
