After sleeping on this, I believe the primary cause of engine failure was low oil. The engine was full first thing, but after going through the valley the first time the engine was 2 liters / quarts low. This engine leaked ALOT of oil.
So when the engine was pulling hard up the hill, number 1 rod bearing was not oiled properly and weakened. Coming back through the valley a couple hours later, the rod had cooled and then heated again. And then failed.
The sad thing is an oil seal and oil pan gasket kit are sitting on my workbench. The water pump and rear axle superceded the gaskets.
