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Originally Posted by Three Peaks
If you had hypereutectic pistons shaved, that may be your problem. From the Keith Black website the article on the hyper pistons says they need the polished tops to reflect the heat back into the combustion chamber and reduce the heat going past the top of the piston to the top rings. This is the reason they are recommended with such a close cylinder fit. If you took off the polished tops without polishing again to factory specs, it may have caused heat to travel to the first ring and cause a ring bind or a ring groove failure.
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Not trying to start an argument here, but I felt compelled to respond.
Although this claim from Keith Black’s website may be technically correct, it is a little misleading.
Hypereutectic has to do with the silicone (I hope that is the correct word) content in the aluminum. When above some percentage, the silicone will no longer dissolve into the aluminum and it forms crystalline structures in the metal. This alloy has a much lower thermal coefficient of expansion than aluminum. That is the reason hypereutectic pistons can be fitted tighter than cast aluminum pistons.
If Keith Black is claiming the polish of their hypereutectic pistons allow a tighter fit than other companie’s hypereutectic pistons, then it would make some sense to me. However in my amateur, armchair General’s seat, after a few thousand miles the shinny piston tops will be covered with a nice black coat of carbon and I have my doubts that this will matter much.