[RedSubmarine]

Looks like the crosshatching is still fine, no honing I’d say. Can you feel those grooves with your fingernail?


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[ProphetPVD]

Fairly certain that "cross hatching" is the result of the cylinder being honed previously:

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.

 

[RoelS]

I just checked them with my attached fingernail, and I couldn’t feel them.
So I guess I’m good to go.

 

[ducvet]

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.

 

[RoelS]

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‘t split the cases yet, so I don’t 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‘t have the dual pickup of the SPS crank. I think (read: I’m sure) that the guy who built the engine didn’t have it balanced.

Thanks for the tip on replacing the bearings; I was on the fence about it, but now I’ll be sure to do it.
I’m 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?

 

[ducvet]

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.

 

[RoelS]

I already have a set of SPS cams installed

 

[final_edition]

i haven‘t split the cases yet, so I don’t 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‘t have the dual pickup of the SPS crank. I think (read: I’m sure) that the guy who built the engine didn’t have it balanced.

Thanks for the tip on replacing the bearings; I was on the fence about it, but now I’ll be sure to do it.
I’m 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.