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Since when did a 383 crank have inherent weaknesses that made it unusable if it had been ground more than 10 under? NEVER.

There are main and rod bearings out to at least 40 under. Racers looking for that last hundredth or two often used to grind the cranks down as much as they could get bearings to fit. The popular 3.91" stroke offset ground 440 crank, or any bigblock chevy rod stroker, has rod journals 0.175" smaller than stock.

I'd say that if your main bearings look that bad, the crank needs to be reground. Period.

And with that amount of bearing material circulating I'd say you need to take the engine down and clean out all the oil passages and everything else you can clean. You can check the taper in the cylinders and the piston fit at the same time. Don't buy any new parts, including the crank regrind, until you know what you have.

Looks to me like the engine was starving for oil. The oil pump is on the front of this engine.
The progressively worsening damage from the front of the engine to the back suggests that for whatever reason there was not enough volume of oil being pumped or else there was oil bleeding out of the system before it could get to the back of the engine.

R.

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