Camshaft wear
Unfortunately, what you are describing is 'normal' for Lycomings. There has been a great deal of discussion over the years about Lycoming pre-mature camlobe and follower wear. There are a couple of STC's out to try and increase the oil supply to the affected areas. These apparently work. I have lost count of how many engines we have had stripped, either for inspection or overhaul, where the camshaft was shot, and well before the specified overhaul time.
Oh, and Lycoming blame everybody else and it is not their fault. i.e. no oil in the engine, wrong oil in engine, revving to max chat from cold, etc
camlobe