This is a pic of the piston I burned at Bonneville. Dual O2 sensors were showing 12.7 until past the 5 mile at WOT, Then indications went very erratic (I saw between 12.5 and 13.1 flash) as speed increased to a max of 231 and rpm stalled at 6400 at mile 5 due to inlet turbulence through the cowl scoop I think. Also due to 2 1/2" tire growth at that spped, altering final drive ratio. This made the fuel air distrubution spread worse and #7 went critical first. #6 wasn't far behind.
I noticed the heat and damage seems concentrated around the gas port holes. Is a gas ported piston more critical for detonation/lean condition? The detonation is furthest from the spark plug.

Biggest issue was I should've lifted at the end of mile 5 but stayed in it after rpm began dropping at 5 3/8 mile or so. Expensive mistake that precluded me from making more runs at Speed Week.
I found on teardown at least one of the middle upper water jacket slots were covered with a sealant film, which coinsided with the hottest part of pistons #7 and #6. Clearly my fault on jetting and not lifting, just trying to diagnose and fix the root cause.
I dropped my intake and heads off at Wilson Manifolds for them to work their magic. I will addrsss the inlet turbulence with strakes and a K&N filter.
Thanks