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How bad are these cylinders?

955 8
I'm in the middle of tearing down my 996 engine, to have the rotating assembly balanced to get rid of a very annoying vibration.
When taking off the heads and the jugs I noticed the following on the cylinder walls:

Cylinder 1








Cylinder 2








I don't like the look of it (especially cylinder 1), but I'm not an expert on this matter. How problematic is this? Can I run it like this, does it need a light hone or does it require a complete replating of the bores?
I would really appreciate an expert opinion on this 馃檹
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Fairly certain that "cross hatching" is the result of the cylinder being honed previously:
Composite material Gas Circle Aluminium Metal


As @RedSubmarine pointed out, if you can't feel any grooves while running a fingernail (an attached one) across the surface of the cylinder then it is probably fine.
 

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Discussion Starter · #4 ·
I just checked them with my attached fingernail, and I couldn鈥檛 feel them.
So I guess I鈥檓 good to go.
 

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Did you inspect the main bearings, your carbon build up is pretty normal toward the top of the cylinder but you notice a clean area why was this area clean? crank movement causing vibration?
rod bearings?
I would change both rod and crank bearings to be safe.
 

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Discussion Starter · #6 ·
Did you inspect the main bearings, your carbon build up is pretty normal toward the top of the cylinder but you notice a clean area why was this area clean? crank movement causing vibration?
rod bearings?
I would change both rod and crank bearings to be safe.
i haven鈥榯 split the cases yet, so I don鈥檛 know the exact cause of the vibration yet. But my guess is that the crank is mismatched to the rest of the rotating assembly.
It is an SPS engine, but the crank has been swapped for a normal 996 one as my ECU is a 16M which doesn鈥榯 have the dual pickup of the SPS crank. I think (read: I鈥檓 sure) that the guy who built the engine didn鈥檛 have it balanced.

Thanks for the tip on replacing the bearings; I was on the fence about it, but now I鈥檒l be sure to do it.
I鈥檓 also considering a 900 SSie crank, to increase the capacity. I have a lead on one, which is not too expensive.

Any other tips as I dive further in this project?
 

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Find some cams.
Last long stroke 900/996 picked up 9 rwhp so not quite 10% bump in power, if you need a crank and will balance anyway then it is a easy decision. add a set of cams and you should have a good desmoquattro motor.
 

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i haven鈥榯 split the cases yet, so I don鈥檛 know the exact cause of the vibration yet. But my guess is that the crank is mismatched to the rest of the rotating assembly.
It is an SPS engine, but the crank has been swapped for a normal 996 one as my ECU is a 16M which doesn鈥榯 have the dual pickup of the SPS crank. I think (read: I鈥檓 sure) that the guy who built the engine didn鈥檛 have it balanced.

Thanks for the tip on replacing the bearings; I was on the fence about it, but now I鈥檒l be sure to do it.
I鈥檓 also considering a 900 SSie crank, to increase the capacity. I have a lead on one, which is not too expensive.

Any other tips as I dive further in this project?
Pick ups are not from the crank but the flywheel and lay shaft gear.
 
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