I had the overhead adjustment done on my previous 02 Marathon H with 110K miles at Detroit in Ocala, FL. They’re known for being bus-friendly, and many people recommend them. As Joe mentioned, I found three clips that had come off and were lying on the head. Although the engine was running fine, I was glad I did the adjustment. It idled smoother and sounded a bit better afterward. The old clips were replaced with the new style, and since it was an H model, accessing the valve cover was straightforward, even with the Jake brakes and higher valve cover. Here’s a comparison of the old and new style clips.