Miata Clack Sound when revving
 

So I been trying to track down this loud clack. Ignore the HLA I just serviced them thinking that was the sound and it was not. Any help is always appreciated.

EDIT. Forgot to add compression 190 on all cylinders and afrs the same no lack in power. When the car cools I'm going to check for anything loose sound louder on passenger

Video no worky for me

Ok well I unplugged the number two cop and revved and the clack was gone. A cycled through the rest and it's only on number two. I'll try fixing the video. But does this mean I spun a bearing?

Video possibly fixed.

I've seen a video of a motor with a bad bearings and the sound would be very noticeable at idle and increase with motor speed. I don't think is a bearing :dunno:

That's what I would think too but another guy on Miata.net said that was a way to test for a spun bearing. Hmmm I'm so confused idk know what to check next but really don't want to pull apart the motor. I wonder if the valves are mess up? I'd imagine if it was I'd have bad compression.

Maybe put the number one cop in cylinder two and leave number one unplugged? Should rule out any strange ign issue. If toyota cops I have had a few fail on me. Judging by the noise, I highly doubt that will do anything but this doesn't sound like a spun bearing to me so would look for a something else.

sounds similar to a spun bearing, but i'd expect the bearing to always make noise.

I honestly think it's resonance.

I switched cops and still had the same sound on number 2. Unless I removed spark from the cyl

Sounds like rod bearing or a broken valve spring causing the valve to float. Time to stop driving and start wrenching.

Sounds like rod knock to me. Well, piston damage, piston ring damage, bearing damage, and/or rod knock on #2. Wouldn't be too surprised if you could rock piston #2 back and forth. With the head off.

Another vid. I have good compression though. If the piston was loose wouldn't I have low comp on that cylinder?

Yes, you would. But I think you can have good compression with a bent rod or a bad bearing.

Doesn't sound like a rod to me. Something smaller. Valve train, I would guess.

my car made a similar noise when I forgot to tighten my timing belt.

but it also idled like shit due to it since the timing was jumping all over the place.

Its tight with brand a brand new tension and idle pulley cause I thought that was also possible the culprit

drain the oil and see if it's got a metallic look. Run a strong magnet along the bottom of the pan and drag it to the drain hole without creating space between the magnet and pan. I'm guessing you're going to find evidence of mechanical failure.

I will try that thanks for the input. i just bought a new magnet the other day too

Well finally found a video on Youtube and this sound damn near EXACTLY how mine sounds and happens at the same rpm range.

Ok so if I replace the bearings. Would I still need to run break in oil as a precaution? If so would it hurt other things or if not could it not let the bearings set in properly?