I was wondering about that valve mark as well. There aren't any lock washers I'm aware of on the motor or turbo, especially ones that would have the potential from getting inside. On piston #7 there is a section on the lower left that seems to me “missing” the soot with some red color which looks odd. By combustion side problem does that include head gasket? Or more like piston/cylinder/injection problem?
Moving over to the passenger side of the block and head (pics below), I have a few valve impact marks in pistons 4 and 6. I’m assuming either the crank bent or something else bent to cause the valves to start opening when the piston was TDC. And strangely a little of the mysterious center valve ring imprinted on the piston too. Along with a red ring on pistons 4 and 8 around the intake valves. Not sure what that is. Also weird is 6 looks cleaner than the rest, with red residue on the head.
IP is a rebuilt 4911 pump that is supposed to be set to standard fueling. In the moments before failure my autometer EGT gauge was <1000. Even when pushing it hard I’ve never had it over 1050. Probe is tapped into the exhaust manifold before the turbo.
I'll lead you know about the heads. I haven't decided yet what I want to do.
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