Strange cylinder wall grooves

[CrazyPrime]

I deglazed my cylinder's today and noticed these strange perfectly straight grooves in my cylinders. Can someone explain how these happened? It is on all the cylinder but #2 is way worse then the others.

Here is #2







This is #1





Can someone explain? This is the first time to my knowledge this engine has been torn down.

[jlevie]

Hard to say, my guess would be broken or stuck rings.

[digger]

Kinda weird that they go all the way to top of bore. I'd say A foreign body could also be responsible as it may have got stuck between piston and bore

[AndrewBird]

Could have happened during disassembly maybe.

[redlightpete]

I had some similar scoring in one of my cylinders. I had left the plugs in for a long time, and on that cylinder the ceramic insulator material had eroded/crumbled off. I suspect that is what caused the damage in my motor.
Still running that 335,000 mile bottom end though, and the oil consumption is low. I haven't checked compression or leakdown.

[CrazyPrime]

Ya it definitely didn't happen during disassembly. I believe it was there when I disassembled my block. My motor had 0 to none oil consumption. I'm planning on just putting new rings in and running it the way it is. Will the grooves be a issue?

[TobyB]

That right there is why you run a good air filter.
It could have happened any time, like, well before you bought it.

If you are building a Pro3 engine, yes, those grooves will cost you.

For a street engine, mehh, you might lose a bit of static compression, but it'll work. Probably well enough.

hth
t

[digger]

personally i wouldnt go to the trouble of pulling apart and reassembling with scratches like that. if you had pulled the head and saw that with the bottom still assembled well fair enough just run it.... they look like they'll catch a finger nail which is a common test

[CrazyPrime]

It will definitely be a street engine. I'm going turbo so a little static compression lose is not a huge issue. Digger would you recommend having it bored? Then would I need oversized pistons? Or just rings?

[jlevie]

It will definitely be a street engine. I'm going turbo so a little static compression lose is not a huge issue. Digger would you recommend having it bored? Then would I need oversized pistons? Or just rings?

Boring means new pistons and rings. You can probably get a better engine with lower miles than what it will cost to overbore.

[TobyB]

In Oregon, I agree with Jim- if you're going to boost, see if you can find something better.

Also, measure your pistons carefully. BMW pistons aren't that durable, compared to the
rest of the bottom end. If they're done, then you get to decide between another used
engine or a new, oversized bore one...

t

[95BMWIC]

If the engine had been disassembled before, then maybe someone didn't debur the piston / rings when installing them - metal filing(s) scratched the cylinder wall..

If it has never been disassembled then maybe broken tip from the piston rings.. (or foreign body as digger pointed out)

[digger]

a good second hand donk seem the way to go

[CrazyPrime]

You don't think it would run the way it is? I mean I ran before with those grooves? My car is an IX so engines aren't as easy to come buy. I'm just wondering if they will have a massive effect and if my engine wont run properly.

[TobyB]

You'll be giving up a bit of power.

How much?

No idea, since it'll depend on how the rings seal up.
And no- one really does any tests for things like this-
they just say 'fix it'.

But not all of us do, and it does work.

No guarantees, though- this is free internet advice, you realize.

t