How long have you owned the car? This may sound far fetched but hear me out

1. Problem occurred after oil change
-this leads you to think this is either coincidence or the oil change has something to do with this 100%

2. The owner told you what oil he used and you tried that with no luck
-if this problem is due to something with the oil change, something still has to be missing

3. Something may be literally missing in the oil that the previous owner used that you did not.
- the previous owner may have used some Lucas oil trestment or "oil honey" to quiet down that very noise you are hearing right now.

If this is your first oil change since you've got the car this seems plausible.

 

I'll give it a try tomorrow for sure.

I actually thought the same thing.. but felt like a conspiracy theorist. This is indeed the first oil change. Unfortunately I dumped the old oil into my garbage mixed oil bucket so I can't get it tested. At least I'm not alone in thinking that!

 

Damn, you answered my next question.

Any update with running the car without the belt?

 

The sound is still there with the belt removed. I noticed it goes away when the car is 100% warmed up from driving. It's most likely piston slap.. Nothing I can do at this point.

 

A little is ok, as long as you get good compression, and your leak down passes I wouldn't worry too much, how is oil consumption? Like I said it could be a loose heat shield in the exhaust.

 

FYI, I found on another site:



" One way to check for piston slap: Remove three spark plugs, leaving number one in place. Crank the engine over until you feel the resistance of number one piston coming up on compression. Crank against compression until the piston is about half way up the cylinder. Now using the fan or main crankshaft pulley, rock the crankshaft back and forth and listen for a metallic knocking sound. If you hear a knock, you have piston slap and the only way out is to rebuild the engine. "



Anyhoo... piston slap from a Honda engine? GM yes. But, Honda? Isn't this unusual, from an S2000, with the original parts in the engine?

 

I performed the "piston slap test" as shown above, heard nothing. Also performed a compression test, (engine warm), and saw decent numbers.. 215, 210, 210, and 220.

If I remove the coil pack on cyl 1, the knock goes away. I'm going to vote bad wrist pin.

 

Yeah. Does sound like worn bearing surface on number 1.

 

Rod bearing you mean? Wouldn't the knock sound a little more rhythmic and get louder when revved?

 

Doesn't sound like rod knock to me at all. Maybe tct needs changing