Hard deposit on cyl. head

[IUPAC]

I pulled the 6.5 from my donor vehicle (reportedly 60,000 mi on a '99 gm crate motor) and got it on the engine stand. I pulled both heads today in preparation for new head gaskets, and after changing my pants (I'm new at this, I forgot to drain the water jacket), I found some small imperfections in the tops of a few pistons (small cracks?). How serious are those? I have a question about cyl. #7. I think I found the source of the blowby, it almost looks like an imperfection in the machining of the cyl. I was hoping for stuck rings. The head above said cyl. has a very hard coating of carbon (I think), a textured surface if you will. Anybody have an opinoin or had a similar experience. The valves look good. Not sure what the bottom end looks like yet. My plan is to replace a 6.2 with this one, I won't be pulling with it and as everyone else says, "I don't want to spend much $."

[Robyn]

The pistons in the 6.5 have a Black anodized coating to help resist heat and down in the racardo bowls that can have a wrinkled look to the finish.
They will get carbon buildup over time though.
Snap a couple close up pix and post for us to look at.
When cleaning these pistons dont get crazy with real sharp scrapers.
A dull putty knife and a wire brush on the head of the piston.
Dont use a wire brush on the ring land area or the skirts.


Robyn

[IUPAC]

Thanks for the reply Robyn, I uploaded some pics to the gallery and will try to link to them here. We'll see if this works.

http://www.thedieselpageforums.com/photopost/data/500/medium/100_2867.JPG
http://www.thedieselpageforums.com/photopost/data/500/medium/100_2868.JPG
http://www.thedieselpageforums.com/photopost/data/500/medium/100_2872.JPG

[Yukon6.2]

Hi
I think you need to pry open the old walet.By the looks of the cyl pic you will need a minimum of a bore job.Though i hate to say it the lower edge of the cyl imperfection looks a lot like a crack. I wouldn't use the piston with the crack in it either.If you can feel any differance in the cyl wall with your fingernail then they are too deep.Get the block hot tanked,check for web cracks,if their are no cracks then you can concentarte on the cylinder wall.
Good luck
Thomas