Weird noise coming from inside the head

[DSM_Aruba]

I just finished building the engine and finally got it to start after a few minor issues.

My current engine setup:
6 bolt short block
JE Pistons (.20 over)
Eagle Rods
Knife edge crank
No balance shafts
Fluidamper crank pulley
BC 272 cams
Stock cam sprockets
BC valve springs
Ferrea 1mm stainless steel valves with Ferrea valve locks
3G revised lifters
Stage 3 1G head
ARP Head studs
FP Exhaust manifold
Greddy timing belt
New aftermarket waterpump
New OEM Oilpump
All new belts (have to adjust one of them, no wonder the squeaky noise)
JDM Mitsubishi Starion Forward facing oil filter housing with external B&M Oil cooler
1G intake
All new gaskets
All bolts torqued to spec

Other stuff:
PTE 5031E turbo
VRS FMIC
Tial Q50 BOV
Tial 44mm wastegate
Magnecore 8.5 mm spark plug wires
ECM Link V3 with Speed density option
GM 3 Bar map sensor
GM IAT sensor
ACT Street/Strip clutch
ACT Flywheel
ACT 2600 Pressure plate


Issue:
Can anyone tell me what that noise coming from inside the head is? It sounds like a diesel engine when you listen close by. It seems like a stuck lifter or defective rocker.

Any help would be appreciated.

Video
YouTube - ‪My Eclipse first startup‬‏

 

[ChiTownHussla]

Faulty iac? Or isc depending on year. Same thing

 

[DSM_Aruba]

I finally got the problem. Piston slap (all four). That's the risk of buying a "build" used short block. Before installing the head I checked the pistons and weren't any play. That's a lesson learned for me.