Manual oil pressure gauge test may be in order as well. You should be able to listen to valve covers thru a yard stick and compare (which side noise from, or even area of the cover noise is from). If it was one rocker arm, should be on one side.

 

I second the drive belt idea, maybe a pulley or an accessory malfunction, just make sure you draw a diagram out on paper of the belt routing to make sure it gets back on exactly right. Only takes one wrench to take it off. Also I would bet that if you disconnected the exhaust at the header it would be so loud it would make it hard to hear the original noise. Worth a shot I guess if nothing else prevails.

 

No, oil is fine. I swapped a new filter on just to be sure. First thing I looked at was to see if i lost all my oil somehow, even though oil light was not on. All good. Also temps are normal, and if oil starved I would expect way higher, right?

 

I would think so. More friction would make more heat, assuming you let it run long enough to generate it.

 

The noise is so bad.
I think the engine will damage if you keep running it.
Agree on oil pressure test.
Your oil light is off - well, if the light is working.
Probably is.

So, the pressure is above a minimal amount.

You can check the chain maybe if you pull off a valve cover gasket and rotate the crank shaft and watch the valves.

Or, just rotate the crank back and forth and maybe you can feel slack in the chain.

If you pulled out all the spark plugs then there is no compression.

and you rotate the crank back and forth it will be easy for a number of degrees and then hard - as it has to turn the camshaft which in turn is pushing up on the lifters, push rods, rocker arms and finally the valve itself.

Well, this is a lot of work for diagnosis.

40,000 miles is not much for a timing chain.
As long as it was put in correctly...

 

Yeah, I'm going to dig a bit more. I think oil pressure is fine. Light works. Even when I swapped a new filter on that day, it illuminates for 2 seconds until the oil flower through. Light goes off right away each time I start it too before. I tested pressure when I got the truck and both hot and cold was fine and well within spec. Still not sure on the chain too, just because your would figure it would get progressively louder or something. But who knows! I will look.

 

OK guys... need some help with my update on this thread. Finally got into taking some things apart tonight to try and track down what the issue might be. Found something, but I need your advice on what it could mean. If you didn't read through the thread, the basics are this: Started the truck and it sounded like a diesel, was running fine before that. No codes, oil fine, etc. Tinkered around a bit, then it wouldn't start at all. Seemed like when turning the engine the exhaust was backing up through the intake.
So, tonight I took the intake off, and noticed that the front 4 ports were dirty while the back 4 were clean. I'm not quite sure what to make of it. I can assume that the front 4 were maybe the ones back up through the intake when trying to start. Before I tear down further, I really want to see what the experts here think the issue might be. There is a video in this thread of when it was running if you want to hear. Only thing I did with the intake after the problem started was to suck seafoam in to try and see if it was an exhaust issue.
The entire intake...ones on right are to the front but I have a close up of each too:


Here is a dirty one from the front close up:


Here is a clean one from the back close up (red flashlight shining into it):

 

Do you think you may have an exhaust leak out the side of the head gasket somewhere (diesel sound)?

My 97 at 180k+ had grime on all 8 passages. Even though I had done several SeaFoams.

But introduction of Sea Foam is not "equally spread" IMHO. Here is a pix, and if it is slurped in thru a vac hose line or PCV line, perhaps it goes into the closer air trumpets.

Have you gotten the valve covers off? Perhaps you oil supply is gunked up (one small passage thru the head to one of the rocker shaft towers).


What does you compression test show, both dry and with oil added (to seal up rings)?

 

No Buzz, I don't think there is a leak from the head. When it was still running I pretty much ruled that oil. Compression was fine prior and no signs of bad. The dirty ones are closer to the ports where it would be sucked in...the seafoam. I think exhaust was backing up into intake when trying to start it...and I'm assuming it is from those ports. But the question is why...

 

By the pics or looks of it, could this be a timing issue? If so, what would that mess up? Looking to see if I should dig in or cut bait.