Hello all, I recently pulled the head on my 91 to repair a noisy lifter. Jeep has no running issues. Found this...(see pics). I didn't go any deeper, just re assembled. Any thoughts?

 

Run it 'til it pukes. Then swap or rebuild. Perfect opportunity to start saving for a stroker!

 

my thoughts as well, just wondered what caused that? Broken top ring? something in the cyl? head,valves and top of piston look ok.....

 

That's probably combustion blow-by from a broken ring, or too wide a ring end gap.

 

How is the compression on the one cylinder? If good, and there was no noticeable ridge, this looks to be a large piece of carbon deposit that bounced around, got stuck between the piston top and cylinder wall, and eventually exited out the exhaust.

Ring gap could never be that large, nor could it travel that high up the cylinder wall; if compression is good, ignore. If it were a metal object, it would leave a shiny indentation and absolutely destroy the top of the piston.

 

Update , I showed the pics to a local machine shop, he agreed . Most likley a carbon deposit. Good to know it may last many more years!