Honing the cylinders!

malcolm;10726 wrote: the block and bore is aluminium and as such cannot run a piston and ring without a coating such as Nikasil or Alusil (silicone as Porsche used).

If the block is bored the coating is gone and has to be 'replated'

If not bored it can be lightly 'touched' or recoated to correct spec.

I have had two blocks bored, and lapped afterwards. I did quite a bit of research before doing so. There is a document, or it is in the manuals how the process should be performed. There is no need for re-plating.

Some people choose to plate a block with damaged cylinder(s) because aftermarket pistons are available. Using the stock cylinders lapped, requires the use of the correct pistons, typically from the same manufacturers that Porsche used in the build of 928s and 968s. Further trivia, the 968 pistons allow the block to be bore for @6.6L when using a stroked crank.

malcolm;10733 wrote: IIRC the special hone and paste required is only availble with a limited amount of suppliers so if it were my block I would talk with someone like Greg Brown in California to get the exact goods and proceed with much caution.

I was able to find local machine shops that could perform the process. I can't say how their work would compare to Greg Brown's. I just wanted you to know if you bring the documentation to a machine shop they will tell you if they can do it. It may not be a process they perform often, whereas Greg Brown would commonly be handling such work.

This may help. It's removed from the cylinder surfaces with a hone jig that uses felt strips.