Mine 5.0 is quiet unlike both 04 mach1's I had after they came up to temp had a tick. Did it hurt the engine NO wasn't nice to hear but it never change in sound. Tolerance stacking of block, head, valvetrain when everything is put together. Exh leak can sound like valvetrain noise. Have seen injectors make a lot of noise before. I do think it's from head cyl after it warms up because being alum it expands. I know from machining alum it may measure out right come back next day blank blank would change. Must machine slowly and keep it flooded with coolant/cutting fluid.
Too true I've also witness the same thing while machining aluminium. The tick of the engine I bought is while its cold after it warms up, its almost unnoticeable. Thats why I'm leaning toward valve train. A bottom end sound you must admit would never really go away and with time would get worse, at least thats always been my experience. I'm just trying to see where to look for. The engine isn't in the car yet. I really don't want to but might remove the pan to see if any of the rods have play, but I have a hunch that i will not find any. I don't believe the bottom end is where the problem lies. Good conversation it bro-thens the mind.