Weird knocking sound from cam gear?
 

So recently my 2000 nb miata started making this ticking/knocking noise from what seems to be the cam gear. The car ran just fine before but it appeared after a drive yesterday.

I first thought the sound was coming from the alternator being loose but that doesn't seem like it.

It doesn't sound like valve lash and I also changed the shims to fix lash already a while ago.

I removed the oil cap, and the cams seem to be getting plenty of oil.

when I rev the engine the knocking sound seems to quite down or even go away but that could also be because other sounds deafen the knocking.

the knocking does speed up when I rev the engine till about 2-2.5k where the sound quites down.

Video of knocking:
https://youtu.be/QO_MuLA9PRs

Could anybody take a guess what this could be? Or any tips?

Thank you in advance!

hard to tell from video.. but check your timing belt tension, can cause a slappy noise if loose

Yeah, I listened a couple times and I'm not sure either. Maybe pull the valve cover and have a look, maybe a shim popped out?

+1 for both of the above
Might be a failed tensioner. Has a sealed bearing missing balls type of sound to me
Valve cover/front timing cover removal next as well.
I might poke around with a mechanics steths a bit but I would not drive it anywhere until it was diagnosed.

Pull the valve cover. I've seen the m6 bolts that hold on the backing cover of the cam gears back off and start rattling into the cam gears, sometimes when they fall out they get slung around the timing belt.

thank you for all the replies, I am definitely going to pull the valve cover. I will check the cam bolt and timing belt tension. I will update this thread if I know more. if you guys have any more pointers to what it could also be, let me know :)

UPDATE: I found the problem, somehow I didn't torque the crank bolt well enough so the crank bolt came loose. because of that my harmonic damper was loose and it started shaking, which, I think, caused my timing belt to wobble a bit and hit the valve cover. making the knocking sound. luckily it was and easy fix and nothing broke.

Might not be the same cause, but my NA knocking sound was because my oil, changed to mobile 1 0w40 and the sound stopped.