Think it is top end &
Maybe worn LMA"s noise.
recheck valves clearance are done correctly.

I didn't listen to it with headphones, but it honestly sounds okay to me. My AP1 sounds just like that when you open the hood and get close. It sounds almost like knock or a bit "diesel-ish" but I think it's just a little bit of lash in the valves (necessary lash as specified in the shop manual). Oh and mine has sounded like that since I got it (22k miles ago) and runs great and comes back with good UOAs. Just pay attention that the sound doesn't change over time and/or get louder as it warms up and you rev. For piece of mind, get a cheap stethoscope from Amazon and see if you can determine if it's coming from the bottom of the block or the head.

Sounds fine to me. What do I know? Not a lot.