LB7: What are these marks in cylinders?

sb62nova · Apr 20, 2013

All cylinders near the top..

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gmduramax · Apr 20, 2013

IIRC its from the heat treating.

JoshH · Apr 20, 2013

gmduramax said:
IIRC its from the heat treating.

Yes, from what I've read, it's from inductive hardening done at the top of the cylinders.

THEFERMANATOR · Apr 20, 2013

Yep, it's the leopard spots as they are called. It is part of thE hardening process used on the cylinders.

http://www.dieselpowermag.com/featu..._made_the_duramax_diesel_engine/photo_06.html

sb62nova · Apr 20, 2013

Thanks for the response. Glad to see were all good.

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AKlowriderZ71 · Apr 21, 2013

I've only had a couple of these Duramax's apart, but they both had the same marks in all of the cylinders. I never knew what it was either.