What cause this?

[Pineapple]

Those are crank bearings. What whould cause such damage on a fresh rebuild engine?

[flex-appeal]

Ouch, they looks pretty bad. The scoring looks like the surfaces may not have been cleaned well enough before installing the bearings. Strange thing is these looks fatigued, are you sure they were the correct bearings? Was the crankshaft clearance measured, if the old crankwas used there may have been excessive oil clearance which would heat up and spoil the bearings.

[fredk]

well, it looks like they werent too tight because the very ends arent no where near as worn down as the middles, I saw something like this where the rods were resized but the holes werent made round again, I guess the same thing could happen to the mains too. You might have gotten the wrong bearings, it looks like the bearing was too big around, do all the rod and main bearings look like these?