Ya might check to see if it has "sleeves". Mine's an '87 and I believe I have pulled a sleeve. Pretty easy to fix, but ya gots to pull the damn thing completely apart! Lotta labor when ya have a bad back, but there's no way I could replace it for what I have in it!
You can tell if ya run a compression check. It's either a valve, which is preferable, or it's a sleeve. Just fixin' the head is pretty simple stuff. If it's a sleeve, yer lookin' at removin' everything includin' the oil pan, which usually on a 4x4 is easier outa the truck!
Eta:
The way diesel prices have escalated, I'm lookin' at droppin' in a big block gas motor. After all, I'll get caught eventually, runnin' my farm diesel in it anyway! Hehehehehehehehe!
Yours must have the 6.9L, mine is one of the first of the 7.3's. They are very similar engines, but I doubt it's a sleeve. I've run into that on some OLD International farm tractors (ever hear of a TD-340?) They had a "dry sleeve" engine. Some of the later "B" engines were "wet sleeve".
My thoughts run towards a dropped valve/valve seat. Back in 2001, when I put a Hypermax turbo kit on it (used), I soon discovered the turbo had a bad oil seal. If the truck idled for even a couple of minutes, it would allow enough motor oil into the manifold that the engine would rev out of control for a few seconds. It could have floated a valve, which would eventually lead to valve failure. It actually topped 4,500 rpm a couple of times. Hopefully, no damage was done to the piston or head.
I've dodged the bullet with "farm diesel" once around here. I came thru one of their road checks on the way to the dump (trash, not DU), and went home the "back way". You would think the "OIL BRNR" personalized plates might have given it away. LOL I have plans to make a "double tank" for possible future checks.
If you use your truck close to home, you could get away with "farm use" painted on the back of an expired plate. Virginia law states that farm use dyed diesel cannot be used in vehicles licensed for use on public roads. Farm use isn't licensed.
