Is this what motor death sounds like?
 

What is the most likely cause of this sound? Started fine after work. Was running a little rough lately. This happened on the road. Haven't looked into it yet. Planning to pull valve cover and oil pan tomorrow.


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Can't tell much from the video but I would check the simple stuff first. Pull the serpentine belt off, start it and see if the noise goes away, if that doesn't help then check the fireplace bolts, sometimes they loosen up and cause a rattle.

Could be something simple... but probably would've been best to shut it off immediately and ask questions later. Does it have oil in it?

If you listen carefully, you can hear the engine saying, "SHUT ME OFF BEFORE YOU DO ANY MORE DAMAGE!!!!"

yes. Oil is within a quart of full. But I didn't think about checking the flexplate bolts. That happened before and my brother was driving it at the time and was gonna sell it to pick and pull. He thought he'd grenaded the trans. When I finally dug into it, as I was getting ready to pull the trans, I found 4 bolts loose behind the inspection plate.

Yeah it sounds a lot like a terribly loose flexplate..... I suppose that's good news if the flexplate isn't cracked?

Wasn't the flexplate unfortunately. I started it up yesterday to try to locate the noise better. Started fine and sounded fine until I gave it some throttle. Sounds like it's in the head when I put on my stethoscope. Wouldn't make the nasty noise until like 1000-1200 rpm, which I didn't do much of. But I'll be pulling the valve cover soon. What kinds of things might I expect to find under that valve cover?