Saw a truck on the side of the road melting down. Poor driver just stood and watched. It finally seized into a smokey mess.

Those are no joke.

I felt bad for the driver. All he could do was watch.

I saw one once and it was unbelievable how high that engine revved.

Wow. Just wow.

WOW! What causes that?

Hitting a gas pipe will do it every time

At work a prototype piece of machinery was being tested in close proximity to the paint booth. The paint booth personnel had picked up a barrel of VMP Naptha/Zylene mix when it fell and spilled all over the floor.

That big Detroit diesel took a big wiff and started screaming inside the building. The mechanics in panic grabbed the first thing handy, a bunch of rags, and stuffed them in the intake trying to choke the engine down. It sucked them in chewed on them and pieces of rags were spit out the exhaust. Finally one guy put a thick piece of card board over the intake and another crimped the fuel line shut and got it shut down.

I was told this had happed years before and everyone ran for cover as the piece of machinery came apart.

In a car/truck with this going on is there a significant risk for the engine breaking apart and throwing pieces everywhere or will the metal just get so hot it melts down and just becomes a worthless mess of metal?

I think either is a possibility.

Wow! I've heard stories about runaways but I've never seen it. That's pretty wild stuff.

I know they put out a lot of torque, but can you not stall it buy putting in a high gear and releasing the clutch... hold down the brake too.

Air+fuel+compression are needed.

Take one away. Tough to do with fumes all around. It’s best to just run like hell.

I had an old Detroit 871 do that to me. Fortunately it had an emergency shut down (a flap that drops over the intake to shut off all the air) that worked. I hated the thought of opening that engine compartment and doing it manually. My next option was to put it in gear and try to stall it (stick shift), I never made it that far. After that I though that duct tape (or anything) over the intakes would do the same as the emergency shutdown if you could successfully plug off all of the air. I did this once to see if it was possible on an engine running at full throttle, it shut it down but it didn't want to quit.
I also had two of them running backwards, interesting sets of events caused those.

My uncle had a brand new, still had paper plates, 2002 F-350 do that to him. We were coming back from Tennessee and had stopped at a truck stop to get fuel. Left both trucks running while getting fuel. Came back out and his was prob turning 6,000+ rpms. Complete melt down, smelled like hell, looked like [censored] under the hood. The trucker next to his exhaust pipe was not pleased at all.

"In a vehicle with a manual transmission it is sometimes possible to stop the engine by engaging a high gear (i.e. 4th, 5th, 6th etc.), with foot brake and parking brake fully applied, and letting out the clutch quickly to slow the engine RPM to a stop, without moving the vehicle."

I have a 1991 Detroit 2 stroke 500 HP 8V92TA motor in my camper and it's computer controlled but the old 2 strokes, the rack would freeze up and run wipe open until it popped if you didn't shut the air off to engine. Shut fuel and it would suck the oil out of the bottom and burn it. Screaming Jimmy's they called them.

Saw an old red cummins run away on the side of I 10 years ago. Smoke crazy high rpm and looking back through the back window of dads pickup I heard it let go and get quiet.

Some of our work trucks have trip valves on the air intake in case of runaway.

My old Brigadier 14 yard dump truck on the ranch with a Detroit Diesel in it will do it occasionally when it's not warmed up. I keep a large piece of cardboard in the cab to put over the air intake to starve it for air when it happens. It is a sheer moment of panic when it happens and you hope to get it choked down before any damage. The first time it happened, I had an old equipment operator show me what to do. He was laughing his a** off and I was having a heart attack!

Looks like an XL, pretty nice camper
The 8V71s that I have had issues with were in Eagle model 10s.