Thank you both for your replies. I think my description as a dimple was misleading, I apologize . The surface in question was perfectly flat with a small hole in the center. The hole was not deep maybe 1/32 and maybe a little over 1/16" in diameter. My understanding as been that both ends of the push rod would be hardened. Checking with a local machine shop, they had never seen this either and did not think it would matter which way the rod was inserted. Apparently the cam makes contact with only half of the rod in order to spin the rod to even out wear.