Originally Posted by
757jonp
In my opinion... (for what it's worth LOL) I thing the actual failure of the cylinder was cause by detonation. I base that on the pictures of the inside of the cylinder in which it shows an unusual carbon pattern. Observe the area surrounding the valves, quite a bit of hard caked on carbon (cooked on oil due to high temp?), but on the other side almost clean. IMHO I think your seeing evidence of pre ignition which literally blasted off the carbon off the clean side just like you hit it with a hammer. I've replaced my fair share of pistons and head gaskets and even a head or two in engines that failed due to pre ignition. In this engine the weak spot just happens to be the jug.
And what about the uneven pattern on the skirt?
Never mind the fact that the "blasted" portion of the combustion chamber is on the front while the "blasted" portion of the ring land is at the rear. I would love to hear your explanation for that
Yes, detonation probably contributed somewhat to the failure but not as much as the misalignment which directed the majority of the stress to the rear portion of the cylinder base.