Cylinder Wall Inspection After Hydrolock Conditions

[Earendil]

Due to a failed gasket (*crosses fingers*) I ended up with a hydrolock condition in one cylinder. 30k miles ago I had the head off and found beautiful cross hatching on the cylinder walls. This time around I find that crosshatch on 5 cylinder walls, while the cylinder that was hydrolocked looks...different.

[Higher res images if you click on the embedded ones]

Pretty cylinder with tiny rust spots and reflections.


Ugly cylinder with heavens knows what.


I'm wondering what I should make of this? The walls have no discernible bumps or scratches, using either my sensitive fingers or my finger nail. I'm not exactly sure I'd do anything about it even if it was a failure, as this is just a tied M20 and I'd probably run it until I had zero compression in that cylinder.

What I'd love to hear (for peace of mind) is "Rub a little cleaner X on there and it'll shine right up!".

[jlevie]

I'm thinking corrosion. I can't tell if there is pitting or if this is just a surface condition. If the latter there should be little, if any, compression loss. If the former, expect some compression loss and rapid ring wear.

[Earendil]

I'll run compression numbers after a few track days, but so far far assembled engine is running well and initial compression numbers came back looking pretty good for it being a dry test on a cold engine: High 147, low 136, so we're talking a 6% difference.

I guess it was just a tiny bit of surface discoloration from the water and it cleared right up after the cylinder went boom a few times.

[TobyB]

looks to me like that cylinder was leaking coolant for a while.
Might be worth measuring the bore- when I had one do that, it wore
the cylinder pretty badly.

t

[Earendil]

looks to me like that cylinder was leaking coolant for a while.
Might be worth measuring the bore- when I had one do that, it wore
the cylinder pretty badly.

t

It's fully assembled (thus the compression numbers) so I can't measure the bore. If it had caused significant wearing, wouldn't that show in the compression numbers?

The miles prior to the hydrolock were a 40 mile drive preceded by a full track day. I have no doubts she took a beating, I'm just hoping the cylinders aren't worse for wear. Time will tell!