As you say, it makes it hard when we jump to conclusions or guess about possible causes and start replacing things without first making a diagnosis.

As far as valve gaps, my experience (admittedly limited) is that most engines hold valve gaps for a very long time and its something that the oem maintenance schedules address. This issue with 06 and later S2ks and migrating valve clearances is somewhat odd and I don't think it the cause is well understood. Some anecdotal evidence that I have read here somewhere might suggest that it is related to modifications - intakes and exhausts. But, why that would be an issue on an 06 but not on an 04 or an ap1 is not clear to me and I am skeptical. I don't think anyone knows for sure.

I have ap1 cars so I'm not terribly concerned about it. One member who drives his car quite hard reports having seen zero migration in an ap1 set on the tight side of the oem spec in approximately 100,000 miles. As far as performance being affected by whether valves are set on tight or loose side of specs, I personally doubt it is significant either way. I'll check mine every couple of seasons so they won't go more than 30K miles without a check. But, I honestly don't think it is necessary on an ap1 to check that often. Its just an abundance of caution. If I get a new s2k it is one of the first things I do. Mostly to set my mind at ease.

I do have mine set on the tight side of the oem spec right now. The car runs beautifully. Pure joy. I may give them a check later this year and see if they have held. Maybe the question of whether to set on the tight side or loose side of the OEM specs is not a one size fits all decision. If your car is not one that is notorious for migrating valve gaps, if you are the type of owner that keeps a close eye on things - you might make one choice. If you own a DBW, or you are not going to be keeping a close eye on the settings, you would probably make a different choice.

 

Your engine sounds pretty much exactly like mine.
I've used a stethoscope and it seems to be coming from cylinder #4 (closest to the firewall) - at least when putting it next to the intake side of the cylinders.

The ticking has been there for a while, although it doesn't get worse, I am too wondering what it might be.

To be honest, I am worried it might be rod knock and I've even bought Hondabond and plastigauge already but I haven't had the time/balls to remove the oilpan in order to find out the horrible truth :P

 

Update:

Before I had a chance to redo the valve adjustment the ticking went away, but the engine still sounded rough to me. I was also experiencing a slight 'puff, puffing' noise from the exhaust, you could feel it and hear it, although very subtly, but it was annoying. I was convinced that my valves needed to go back to mid range and not the tight end, especially the exhaust ones. She just didn't sound good to me at all.

The fine gent who came over to assist is well known to the Arizona S2ki community for his stellar precision work, he set my valves back to right in the middle spec, we did a leak down down and compression test along with bore scoping the cylinders which showed a very, very healthy engine all around. After the new VA, the engine sounds much, much better, way less chatter, and the puffing is gone (even he didn't believe a VA would work, but it did).

The next day, engine is sounding great, no puffing and the ticking comes back for a few minutes. As a result, I called her some very dirty names that would make a porn star blush. She hasn't ticked since.

Theory in this case is that after the valves (which were in spec anyway) got adjusted after so many years, they could have started ticking due to the new seating, and needed time to find themselves anew with the new adjustment. It's hard to specifically say, but I've never been a believe of setting things on the 'tight end' of the range as there's no statistical proof (dyno or otherwise) that it does anything for performance.

It's been a month since the work was done and she's back to normal.

 

I'm glad you are running good now.
I'm sorry, but I have a tough time believing that your valve gaps are causing any of the problems you were having when they were set within manufacturer's specs, only on tight side of the spec. That part of this makes zero sense to me.

 

I agree. I unfortunately made an error of misunderstanding the feeler gauge measurements I used the first time I did it a week ago but that caused me to have set the valves way too loose. Now we know too loose is not a threat to anything apart from excessive noise. I redid the VA the next day with the correct gauges choosing the tighter side of the OEM spec (also recommended by Billman) IN: 0.008" EX: 0.010" and its quieter now. They're probably still setting into their new setting. Car drives great! Still monitoring it as I go but the various VA "noise" experiences has me paranoid lol. The injectors definitely exhibit a ticking sound of their own. As for the VA specs, OEM tells you 0.23mm IN and 0.27mm EX +-0.2mm either side which means you're safe if you choose the tightest or even loosest side of the spec. My fear was that the valves were beyond the acceptable tightest side of the spec so I had to make sure myself.

The slight random "puff" sound during idle the OP mentioned is there for mine but not always. This is what made me want to do a VA on my own to rule it out. I seem to think there might be a little vacuum leak somewhere.

 

It's ok if you don't, but it doesn't change the fact that it did change, and multiple people bore witness. Immediately after the VA in December these problems occurred, I noticed it right away, and immediately after the next adjustment last month, it was immediately reverted, especially the exhaust 'puff puffing'. Much to the surprise of everyone (but me). My foray into this started a few years back, in this thread link below, start midway where I resurrect an old thread and ask a bunch of questions. Basically my intake and exhaust were on the tighter side, they were too tight and the idling was off, louder, wasn't as smooth and when I needed to give it gas in the city to make a turn I didn't have normal low end power like before.

https://www.s2ki.com/forums/s2000-un...-937416/page2/

After that I always had the VA right in the middle of spec. Because it 'feels' faster doesn't make it so. I've seen very little data that shows the benefits of putting them on the tighter side. I've seen some dyno numbers but there was a trade off on low end power plus the risk of toasty valves.

This being my daily driver for 14 year, I notice every single new noise or change in the car, coupled with having the hearing like a dog, it's a cursed blessing with these noisy cars.

Take it with a grain of salt, but to others looking for solutions to strange low end power issues, puffing of the exhaust (that isn't an exhaust leak), or rather noisy engine, try adjusting your VA to dead center on intake and exhaust and see if that helps like it did for me.

 

I'm just not keen to pull the cover again and adjust them to middle of the spec to see if it completely eliminates that slight random puffing... but maybe I should do it asap since you say it actually worked for you. I set my valves to IN: 0.008" and EX: 0.010" last month.

Have you ever run engine diagnostics when the puffing occurred?

 

I believe that having the exhaust valves too tight causes this. We did check the compression, leakdown and also bore scoped the cylinder walls and everything checked out great. We were also going to bore scope the valves from the manifold but I didn't have the right gasket so that was aborted. I didn't check to see if any codes were being issued. Re: the puffing sound, you can google tight exhaust valves and popping / thumping / puffing sounds at idle and find some interesting information. I'm not saying that this is exactly your issue, but if you've ruled out that you have an exhaust leak, or don't want to spend money replacing parts that may or may not be your issue, checking your VA is a cheaper alternative. I wish you luck!

 

Thanks!

So I found the issue. After a spirited drive the random puffing during idle was there as usual. I decided to unplug the MAP sensor and voila! Idle was perfect, not one single puff. This obviously means I need to replace it since I am unsure whether a simple whack would help it. The CEL immediately went on so I cannot drive it with the MAP unplugged but I'm looking for a new or good condition second hand one to swop out asap.