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full quack full quack is offline
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Hey there,
I do not think this was caused by detonation either. Looking closely at the photo's, you can clearly see the scrape marks on the piston crowns, where the valve has impacted the piston.

Furthermore, you can see the outward crack progression on the intact section of the piston crown. There is no sign of detonation melting at all, all piston edges are still sharp, as are the edges of the fracture points. If nothing else, the fracture point edges should at least show some signs of excessive heat, but they do not.

I believe what you have here is a simple machanical failure, caused by cam index shifting, resulting in piston & valve contact.

I would at least drill & pin the cam sprockets, once proper timing has been established.

My .02 worth.

Mark
Old 10-07-2011, 06:38 AM
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