I did unplug injectors (not coils) to check if it was a rod bearing issue. This is a common troubleshooting technique for checking for rod knock, when a cylinder is deactivated you remove the majority of the load from that rod. This makes the sound go away when you deactivate the offending cylinder. I unplugged injectors as to not flood the cylinder with fuel.

But all of this may be a moot point...

Jmpu671 may be right on the money. I did a track day on Sunday and all seemed good. Ran four 20 min sessions and on the last one I noticed just a bit of hesitation above 7k RPM through turn 8a at Sonoma (high speed right-hander). After cooling down in the paddock and starting it up to go home, the ticking was suddenly much louder. I decided to drive it home and noticed that it ticks most on decel and idle but I can still hear it on acceleration.

The plan now is to drain the oil and send a sample to Blackstone for analysis to see if they find some of that fools gold!

 

Makes sense, thanks for clarifying. If it is a spun rod bearing that would be really sad, especially since there does not seem to be an obvious reason for it to occur.

 

Bearing clearance could have been marginal as it was. In any case you don't need to remove the engine to replace rod bearings. Main bearings yes. Plastigauge is cheap checking rod bearings is free besides the cost of gasket maker. If it is rod bearings it's not too expensive to fix and your car will be good as new. The more you push it the worse it'll get.

 

If it's indeed a spun bearing, I blame myself. The day before the ticking started, I installed a freshly powdercoated valve cover that had been sand-blasted before coating (mentioned in original post). If that's the case, I don't know if I could ever install another baffled valve cover that had been sandblasted...

An oil analysis should tell the tale.

 

You could have had a detonation event take a marginal bearing past the point, it doesn't necessarily mean it's spun. If you're lucky and it's just a rod bearing you can fix it pretty cheaply.

 

I once had a valvecover that was bead blasted, for peace of mind I decided to wash it out before installation and I was shocked how much grit came out of it. Plus all threaded holes were jam packed which killed some of the threads and I had to clean them out with a tap. Never getting that done again.

 

I'll keep my fingers crossed...

 

Any updates here?

 

Funny you should ask! I've been focusing on my 260Z lately and hadn't touched or driven the S2000 since the 9/11 track day. Today I finally drained the oil and got a sample which I'll be sending out to Blackstone tomorrow. The results of the oil analysis will dictate the path I take.

 

awesome.