Quote:
Originally Posted by scheides
Haven't checked the turbo for shaft play or anything but did look pretty closely at all of the fins on both wheels and w/o removing the covers to be sure, they appear to be all there.
Just talked to Shawn (simulatedwood) and he's leaning towards TTP's theory where the rings are gapped to tightly from the factory. Running good (high) timing for extended periods causes EGTs to get high and the pistons/rings fully fully expand causing the cyl wear that can be seen on all cylinders. There doesn't really appear to be detonation pitting on top of the pistons (maybe I should go take closer pics of all piston tops to verify), and he said that perhaps the knock I was seeing was induced after the ring failed.
He's the second person to mention 'cold seizure' on snowmobile engines where the piston warms up faster than the cylinder wall/block, causing a similar outcome.
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TTP's theory is interesting, but most other shops seem to disagree with them. I am not sold either way, but apparently the 4g63's have similar tolerances so who knows. I hate the idea that TTP could be right though, lol.
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