92 GSR, B17a engine rebuilt about 7k miles ago with all OEM components (basically same specs as an ITR engine but with 1.7l instead of 1.8). The car is a track toy and the engine has been very strong and reliable for the past few years since I put it together. Coming home from the track last month I noticed a strange ticking noise that starts at about 2k rpm and continues till at least 4k rpm at which point it stops or is drowned out by other engine/exhaust noise. Been troubleshooting this for a couple weeks as I've had time, didn't used to make the noise when stationary and reving the engine, but just today I was able to get it to tick while stationary and searching for the noise under the hood.

Here's what I've tried so far:
- no loose/rattling heat shields, body panels...etc
- not wheel/tire/suspension related
- not vss related
- adjusted valves
- checked LMA's and they feel smooth
- doesn't seem to be the injectors
- tensioned timing belt
- nothing fishy looking or loose in the valvetrain that I can see

I did the screwdriver-to-the-ear test and I can't hear it coming from the trans, head, block, or IM. It sounds like it's originating from somewhere between the engine and firewall. The only things I can think of now that are in that area are the IACV and alternator. I did notice a small leak from the IACV so I'm going to pull that off next. Yesterday I taped my phone into the engine bay to try and record the noise, you can hear it best just as I start to accelerate before the noise either dissipates or is drowned out by other noises:
At this point I'm pretty baffled and just worried it may be something serious which could result in me not making it home from the track this weekend without a tow truck Any input or suggestions would be greatly appreciated. Thank you!

 

I am exactly in the same boat and CAN'T find the problem!

 

I heard someone had the same sort of problem and it was a spring broken tensioner spring with timing belt!!!

 

Mine turned out to be rod knock and the outcome was: