[Henry Schmidt]

Originally Posted by E Sully

. https://www.qscusa.com/products/porsche-911-86mm-aluminum-nikasil-coated-cylinders-pistons-set
Henry Schmidt used to sell them, but I think quality can vary.
https://forums.pelicanparts.com/porsche-911-technical-forum/312904-qsc-cylinders-anybody-ever-use-them.html

The 86mm QSC Nikasil cylinders were designed incorrectly and this design flaw can result in catastrophic failure.
After the first failure (during a standard break-in process) we sent the failed product to an aircraft company for non-destructive critical analysis and they determined that the failure was caused by an impact (maybe dropped) after the manufacturing process.
The next set we tried was carefully inspected before installing. The second set got past the initial break-in but failed on the first test drive.
The second set suggested that the issue was manufacturing so we got an engineer to analyze the cylinder. He found the flaw. The cylinder used as a sample for the casting was an 84mm cast iron cylinder. That cylinder has cooling fins that go all the way to the base.
Those fins create a very this area at the base when it is bored to 86mm. Reciprocating loads cause the cylinders to crack along one of those fin grooves.