Thanks for all of the tips guys. I pulled the valve cover back off and re-checked them with the lobes pointing at the oil pipe. Most felt fine, but the first valve felt fairly loose and a couple others were questionable, so I readusted those and made sure all of the lock nuts were tight.

Once I did that I decided to clean the gasket surface. While going around, I bumped my hand into something I hadn't noticed, there was a loose object sitting behind the first bearing bridge. I thought I had broken something, but when I picked it up, I found it to be half of a hood release handle that had broken off! At first, I thought maybe it was the current one, but I looked up and it was still intact. I realized that someone must've broken the handle and accidentally dropped it in the oil fill hole, and amazingly enough, it just sat there and didn't destroy anything. I carefully looked for other pieces, but didn't find anything.

I don't think it was the cause of any ticking or anything, but it was crazy to find that sitting there. After re-assembling everything I took the car for a drive, I was able to detect a very light noise at first, but after a drive, it was not their. Now the car runs much quieter and smoother. It still has an injector hammer at low temp, but that's for another day. However, at warm, operating temp, me and my friends were in amazement of how much quieter it was running, and how much less it was vibrating. And honestly, I was able to pull it apart, check the valves and re-assemble in less then an hour. I encourage anyone who hasn't done that to do it asap!

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1984 Mercedes-Benz 300D