Mystery Engine Rattle - SR20DET

Please post a comment if you have any insights!
It becomes quieter once the engine warms up. I've bled the lifters multiple times, and they all seem to be in good, solid condition. Definitely sounds like it's coming from the head, but I can't be sure - hope it's not piston slap? Perhaps the valves need to be re-shimmed?

The bottom end is rebuilt with forged pistons, and each cylinder makes ~160psi compression. Replaced water pump, oil pump, cam sprockets, chain tensioner and chain guides.

[serial]

It's possible it's just some light piston slap on account of the forged pistons. Generally when that is the case, the noise is loudest either at the top or bottom of stroke. If you have a stethoscope to listen it would help isolate where it is actually coming from..

Piston slap like this isn't going to really do that much damage provided it is gone once the engine reaches op temp. Were these pistons standard bore or oversize?

[CherryGarage]

Just read the comment that you sold the car. But I have one big question. What brand timing chain did you use?

[canadianssrdet]

Just checking if you ever figured this out?