Originally Posted by AJ@ESS
We measure the cylinders to ensure proper specification before assembly. If any problem is found a new block will be sourced. Boring and rehoning a Alusil cylinder is a process which rarely ends up well in terms of cylinder seal quality. Sleeving can be done, however there are several drawbacks and potential issues with installing sleeves in an engine like this. The best solution in our opinion is to reuse the stock Alusil bore, retain the structural integrity of the block and run custom designed Mahle LC pistons designed for boost with OEM grade PWC and piston coating. It is an expensive solution, but the end result is an engine that runs like a stock motor with no durability compromises or excessive oil consumption/engine noise.
Ive taken multiple bmw engine apart well after 100K miles, you can still see the original honing marks on the cylinder walls almost everytime. You will usually see conicity if you have some wrist pin issues early on.