I'm swapping the heads on my 2003 2500hd 6.0 4x4, took a closer look at the cylinders today while the heads were off, and I noticed some spotting on one of the cylinders - pic below. This is from passenger side.

If you run your finger over that area, you can feel it's off, not much, but there's some wear there.

Wanting to get a feel for whether or not I should just pull the engine and do a complete rebuild - I wasn't planning on it, but if I'm going through the trouble of everything else, then I'd rather do it now.

Hoping someone more experienced than me can tell me how bad that really is.

 

Are you asking about the bore wear or the grit looking white stuff on the pistons?

The shiny spot on tbe bore doesnt look bad at all. I wouldn't be worried about that

is the white stuff burnt coolant?

Zooming in, there is debris in that hole between the piston and the wall. Make sure to clean your motor out real well before buttoning it up. If the pistons are ok, and the thing wasn't having a compression miss before this; I'd run it

 

All see there is, water (coolant?) has collected in there and sat for awhile.

Water, probably rainwater. Coolant, probably a gasket leak. Figure out which of the 2 it is and FIX IT. See to it that it doesn't happen again.

The damage to the cyl walls though I don't think is serious. As long as the root cause is FIXED. The root cause is possibly serious, the damage at this point it is not.

I would NOT in any case whatsoever "rebuild" it. LQ4s are entirely too cheeeeeeeep and plentiful for that. If all you're doing is repairing your truck to get it back working for you again, and you have ANY DOUBT WHATSOEVER about THAT particular short block, like if you suspect the bearings rings etc. are damaged as well, just throw it in the trash and get another. DO NOT mess with a "rebuild".

 

In the truck, I would try WD40 and red scotch brite. Rub in the direction of the crosshatch.

Out of the truck, I would pull the pistons and run a ball hone through it then clean it.