When you get in a hurry, some things happen.

Way back when my engine was being done, I forgot to order hardened push rods for my upgraded camshaft/rockers/springs. While looking for that strange noise, decided to pull a rocker - oops, the regular OEM push rods are galled - and my guess is that they flexed and contacted the head. And no, with a mild hydraulic cam and fairly 'light' springs, guide plates should not be really needed.

Now - that strange noise - might have just been a very loose water pump pulley. Since I can barely get to the flat socket head screws with an allen wrench, there is no Loc-Tite on them - so if that fixes my problem, it will just be a regular maintenance item. If it's something else, and internal to the engine - it might just get interesting (read that as expensive as well as time consuming)