I tore my engine a part and noticed staining on the combustion side of the all the housings. Like a carbon staining or browning from the leading plug all the way to the exhaust port. Both rotor and side housings are stained. I don't think this is normal as I have not seen this on my other teardowns. Chatter marks on also there. This was a stock motor with approx. 130Km (90k miles). Motor was in good shape, not blown.

I think the car was obviously running rich. I guess I'm just looking for other peoples observations or comments.

 

Is it possible that the motor was carbon locked at some point?

 

No the motor was running perfectly fine before teardown. Car even ran high 13's at the track (it was an FD).

I was able to clean most of it off the rotor housings but the chrome on the side housings is actually stained. Weird, maybe I'll post pics of the side housings.

 

I had that on my 12a, wasn't as bad, but I couldn't figure out for the life of me what the hell it is. Most of mine came off with some gentle scrubbing and a tad of carb cleaner.