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911nut 911nut is offline
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Join Date: May 2001
Location: Michigan
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Quote:
Originally Posted by JFairman View Post
I see signs of detonation on those pistons. It's showing up as fine pitting erosion in the aluminum mostly around the edges of the JE piston and in the edges of the valve pockets.
Jim, since there were pieces of piston bouncing around in the combustion chamber (some which passed out through the exhaust valves and on to the turbo), that is the most likely cause of the pits that you see in the photo.
Sometimes the damage is so extensive it can obscure the root cause of the failure. In this case, however, there isn't substantial shrapnel damage, which can simplify the investigation.
As for the cog slipping, that most likely have been the result of an overrev. I didn't realize that both banks of valves had kissed the pistons.
Trond, it appears that your buddy owes you an engine......
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'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb

Last edited by 911nut; 10-09-2011 at 06:06 PM..
Old 10-09-2011, 06:03 PM
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