Strange marks in cylinder wall

[JFairman]

Hi, this is the number 5 cylinder from an '87 911 turbo with some strange marks in the cylinder wall.
You can see the nikasil coating has chipped off in a couple places up at the top and I think that was caused by detonation. I could hear high frequency crackleing or pinging like detonation while accelerating hard when this cylinder was part of the motor.
The rest of the cylinders looked good and the pistons all looked good. The ring lands were all in good condition and there were no broken piston rings. I still have the rod bearings that were in the motor at the time.

I rebuilt the top end of the motor with new Mahle 3.3 liter pistons and cylinders a year and a half ago and it has been running great ever since. I always use 93 octane unleaded and that's the best we have here in S.Florida.

The weird thing is these lines in the cylinder wall going from top to bottom. They are not perfectly straight and don't really look like pieces of broken off nikasil made them because it seems to me the lines would be straight. You could feel them a little bit when dragging your finger nail over them.

I'm just wondering if anyone has ever seen cylinder wall marks like this before and does anybody know or have any ideas what made them?
Thanks in advance for any replies.

[DSPTurtle]

Jim, take a ride up to Melbourne. I pulled a little motor apart with some seriously interesting marks in a cylinder last night.
Do you remember if the piston was at the bottom of the bore when you pulled the cylinder off?

[JFairman]

That would make a nice little road trip.

I don't remember the piston positions in the cylinders when sliding the cylinders off. It was a year and a half ago too.
I just laid a rag across the bottom studs so the pistons had something soft to lay on.

According to the thick folder of receipts that came with the car when I bought it 9 years ago the top end of the motor and the transmission were rebuilt or overhauled at the same time around 30,000 miles before I got it. The motor parts replaced back then didn't include new pistons and cylinders. Rings, rod bearings, valve train parts, and stuff like that were replaced.

[DSPTurtle]

Since its lookalike they're are at about 9 o'clock on the cylinder I was thinking maybe a little carbon got dislodged when pulling the heads and got wedged in the ring as you pulled up on the jug. Are they superficial or can you feel them with your fingernail?

[JFairman]

I remember you could feel them a little with your fingernail. The marks were definately there while the motor was running. The pistons were all in really nice condition and there was no marks or scratches in the sides.
I think this one cylinder already had these marks when the motor was overhauled at a place in Nashville, Tennessee in March of 2000.

The guy that bought the set from me 1.5 years ago has probably had them bored and replated by now. I could ask him.

[Tippy]

So no broken rings?

[JFairman]

Rings were all intact and in good shape. It ran well but that cylinder burned a little oil and had a little lower compression.
The rod bearings were dated 07-99.