Piston ringland damage

[500orbust]

Has anyone seen this type of damage before? This is a ross stroker piston for an evo 8.

[97 4G63]

Nope ..
But you need a new piston.
That almost looks like a new piston what happened??

[bluegs03]

wow that almost looks like it was machined wrong or something??

[500orbust]

This happened to all 4 pistons. Machinist / engine builder thinks that its most likely from not letting the engine warm up fully before driving hard. There are no signs of detonation on piston, head, spark plug, or rod bearing. This isn't from my engine...thank god. Just trying to get some opinions.