That's really bad news.

You do see complete (relatively low mileage - 60k,) used motors for sale under $4k, which I would guess would be cheaper than a new block and a set of rings from BMW. Save you a LOT of work and some cost, (gaskets, bolts etc.) on reassembly.

I guess you could find a used shortblock, but that might be really tough to find. I'd still hone it and put in new rings if you find one.

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2014 BMW 328i Xdrive
2011 BMW 335i M-Sport
2008 BMW X5 4.8i Sport
2000 BMW 528i 5sp