What in the, do I really want to know noise is this. Nissan VK56

My 2012 Armada has a noise, little hammers on steel kind of a noise.   It is not a good noise, internets are dumb kind of a noise.

Not when the engine is cold, not when I have been driving for a few minutes.  Most pronounced when the engine is warm but has been setting for a while, then asked to run again, not at first but only after 1/4 -1/2 mile of driving.  This follows engine rpm but only from 1800-2200 roughly and only under a specific load, less load and it goes away more load and rpm increases past the point of noise.  After the initial noise, that if I'm careful can keep it going for about 5 very long seconds, goes away and doesn't return until the next rest cycle.

Oil and temp gauges read properly, oil is full and changed regularly with proper weight synthetic.

Sounds a lot like a cracked flywheel on an old Chevy that is trying to impersonate a rod knock.  Also very reminiscent of the old Vortec and 4.0 jeep cold piston slap.

Ignoring it has not helped it go away but that will not stop my from continuing down that path. 

Chain tensioner?

Lifter out of adjustment?

VVT issue?

Cracked manifold?

In reply to akylekoz :

These were known for having issues with exhaust manifold cracks/leaks. Since it only occurs in a narrow temp range, that's my guess. Though I thought they got better manifolds by 2021, but I guess any manifold can crack. 

I'll check for cracks next time it's on the lift.  My old Pathfinder had the same motor, it would tick when cold then go away.  Different sound but maybe cracked in a different place.