Major Piston Damage!

That's one ugly piston, Joe.

I've had a couple 4.0L Cherokees, and they will run on a prayer it seems.

I had a similar incident with my F250 a couple years back. Pushing it way too hard, with the camper on, coming home from a 15 day/12 hr per shift at the pulp mill. Only about 2000 miles on a fresh, hi-comp, 40 over rebuilt 460 running on propane. I was running 20/50 in it, mistakingly thinking it would be a better oil. Well, it started detonating, and then ran like crap for the rest of the trip home. Luckily it was only another 20 miles or so. Got home and found which hole was bad, pulled the plug and it was coated in aluminum. Checked the compression and it was still fine, thank god. It's been running fine ever since, but does have a very slight knock.

I still have the plug, I should take a pic and post it.



Oh, and those exhaust manifolds almost always end up cracked on the 4.0L. Must be a bad design.