Quote:
Originally Posted by VictorH
I'll going to second and third what Track Rat has already stated. You have detonation until proven otherwise. Anyone who's run a boosted engine and gone lean will recognize this damage pattern. Obviously you're not boosted but detonation in a n/a motor will do the same thing. Yes, it will scuff your cylinder walls, break your pistons and ring lands as well as scuff your bearings as you are subjecting the cylinder to really high pressures (basically uncontrolled explosions). I've seen this enough times to say it's detonation as cause #1-#3 until proven otherwise.
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That could very well be one of the reasons on what has happened. An overheated spark plug (too hot a heat range for the application) as seen from my plugs could also be the reason that has led to this. Glowing carbon deposits on a hot exhaust valve (which may mean the valve is running too hot because of poor seating, a weak valve spring (a few cases of S65s having weak valve springs) or insufficient valve lash) could also be another reason as I had to replace about 5 of the valves that were badly burnt / bent. Take note that my RPM limiter was untouched.