Every piston got hot. You can see where material is missing on each piston. It evaporated.
This engine may have had gasoline in it. No one would fess up. I don't think it had a fuel tank on it when it arrived at our shop. There was definitely something screwy going on, and no one was talking.
The head was also trashed. It looked like an oxy/acetylene torch was used to burn holes between the exhaust valves and valve seats. The harmonic balancer, HPOP, and flywheel survived, and that's about it.
This failure's magnitude is certainly an outlier, but the C7 (in my opinion) still has shortcomings that are inexcusable. The parent bore block being the worst part. The super hard, brittle piston rings break and shred the relatively soft block. The valves have an annoying tendency to have their heads snap off if there's any guide wear, if they aren't adjusted perfectly and on time, and leaking injector tips definitely raise piston crown temps to unsafe levels.
Luckily the aftermarket has a lot of these problems solved. There are US-based companies that offer pistons that are higher quality with rings that are more ductile and don't break, and they wear the bore much less, and valves are available that are better built and are much tougher. LA Sleeve makes a cylinder sleeve that is tough and hard. That matched with a nice ductile ring means many many miles of consistent performance and little wear. The expense to switch to these parts is still significant, and working on a C7 in the M2 chassis is an exercise in patience.
like this, I tell ya.
