Honing the cylinders!

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22 Aug 2012 13:40 #10394 by denhamfly
What is the correct paste to use when honing out the 928 cylinders and where do you get it?:confused:

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22 Aug 2012 14:16 #10396 by srshaw3
Replied by srshaw3 on topic Honing the cylinders!

What is the correct paste to use when honing out the 928 cylinders and where do you get it?:confused:


My research and experience in the past is that the process is called lapping, and is different than honing. There are machine shops with the correct equipment.

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22 Aug 2012 14:44 #10401 by 928mac
Replied by 928mac on topic Honing the cylinders!
I thought that after it is bored they acid wipe the bore to eat away the aluminum and leave a hard silicone face.

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22 Aug 2012 15:37 #10404 by midlman
Replied by midlman on topic Honing the cylinders!
careful with the info over here guys.. Alusil is not a coating..it is the material that the block is made of (hypereutectic aluminum silicon..see the wiki en.wikipedia.org/wiki/Alusil ). Nicasil is a coating (nickel silicon) that can be used on an alusil bore and it is also rock hard.

The 928 block had special heaters in place during its formation to allow more silicon to be present in the bores of the block. Once it was set, it was bored and then a special machine/paste (sunnenhone machine ) was used to expose the silicon crystals in the face of the bore. This is what the pistons/rings ride on and its extremely hard and wear resistant. One can easily expect over 300000 miles from a 928 alusil block.

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.

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22 Aug 2012 15:45 #10405 by denhamfly
Replied by denhamfly on topic Honing the cylinders!
If the spec's are good and you put new rings get in it and go?

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22 Aug 2012 15:50 #10406 by midlman
Replied by midlman on topic Honing the cylinders!
If the bore isn't scratched or gouged then that is what I would do.

If the spec are good and you put new rings get in it and go?

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22 Aug 2012 20:35 #10422 by srshaw3
Replied by srshaw3 on topic Honing the cylinders!

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.

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22 Aug 2012 21:30 #10429 by srshaw3
Replied by srshaw3 on topic Honing the cylinders!

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.

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16 Sep 2012 23:14 #11271 by atb928
Replied by atb928 on topic Honing the cylinders!
This may help. It's removed from the cylinder surfaces with a hone jig that uses felt strips.

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