The same debate about boring, or even honing, Nikasil or Alusil cylinders has been around for decades in the Porsche community. Mahle made the Nikasil barrels for the 911 engines and KS made the Alusil. There are those who say you can't do anything to the bores on the Nikasil barrels, but there are a couple of companies who have introduced a process to recoat the bores. Alusil is similar but there are more people who say that it can at least be honed.

I know that in an old 911 engine with Alusil barrels that I had about 20 years ago, I honed the bores and it took forever to get the new rings to seat. I finally gave up and bought a used set of matched Nikasil pistons and barrels with a larger bore for increased displacement.

My current 911 engine is at the machinist to have the crank balanced and polished, and to have bigger valves installed. He's also got my Nikasil pistons and barrels. He said that I still have a good crosshatch on the walls which is good because in his 30+ years of building street and race 911 engines he's never had good luck machining a Nikasil bore- other than on pure race engines that were torn down after every race.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R