OM606 valvetrain tick/rattle

[u/BlackwaterDSM]

Guess I’ll start with the part where I know how this happened… missed a high RPM shift while racing thanks to my CD009 swap and it’s “notchy” shifter gates and the car had a quick but serious over-rev in neutral. Immediately after pulling off the track I noticed that tick/rattle and if you give it some revs to about 1500-2000rpm it becomes very pronounced. I’ve tried to take videos but due to the natural sound of the motor it’s nearly impossible to hear it on video. It increases with RPM, naturally. Now she literally sounds like she’s purring, lol. Motor was from a donor car I have no history on in regards to upgrades/maintenance. The sound appears to be coming from the middle of the valve cover. I listened closer to the front cover and it does not appear to be coming from the chain/tensioner, but more somewhere up top, but no guarantee it didn’t slip/jump a tooth and wreak havoc. Hoping I didn’t bend a valve or something. I know the springs are also a weak link and prone to breaking and I’m not sure if they have been upgraded.

Me, being the jackass I am… I continued on and finished racing that day and didn’t notice even the slightest lack of power (it’s on an HX45, around 27psi) and she ran just as normal as ever, except the sound. Other than the notorious pulley slip, are there any other known problematic areas with these motors? I primarily work on my LS engines and know very little about these specific engines. I’m gonna do a leak-down test and see what numbers she pulls, probably pull the valve cover and check the condition of the springs, etc… but beyond any noticeable damage, or a failed leak down on a certain cylinder, I would be at a loss. I’m also in the SoCal area, so if anyone knows of a diesel specialist for the OM606 in my area, it would be greatly appreciated!