Yep. Number 3 rod bearing was gone, scored the crank up pretty good too.

I checked all the rod bearings and they are all varying levels of bad, all showing copper, a couple with light grooves. Number 3 was the only one that grooved up the crank though. Tried to polish it out a little with some scotch brite but they're too deep.

Stores were closing and no-body had the bearing on hand anyway, and the truck couldn't stay ramped up half in and half out of the garage because it was preventing me from closing the door. I ended up putting it back together, leaving all of the current bearings in except number 3, which I swapped for a used bearing out of the core motor I bought for building the 408 (that bearing is also bad, but not nearly as bad). Test drive revealed that the primary clatter is gone. Massive improvement. There's still what sounds like some very light valvetrain noise if you push it up over 2500 and hold it there. Just a hair more than I recall being normal when this engine was healthier. Either that noise is the sum total of most/all the rods just ever so slightly knocking, or more likely, the worn out bearings are causing the oil pressure to drop enough that the lifters can't maintain all their preload and that's the noise that remains. Scanner shows 60psi, but the sending unit could be lying to me, I haven't checked it with a mechanical gauge yet.


Honestly, this is good enough. For now the truck just needs to be able to be moved for mowing and be available for "emergency duty", like if my daily is down and I need to run to the parts store or something like that. The tires are so dry rotted I half expect them to pop any time I drive it anyway, so even with no engine issues, it wouldn't get driven much until the tire issue is resolved...which I am not going to do until I get ready to put it back into more regular service.

 

Yeah, I can see how that might generate some noise.....

 

I'm honestly a little surprised the bearings are so bad. I am quite meticulous with the maintenance on this thing (though I guess I have no idea what happened to it before I bought it at 130k). Clearly the bearing has passed some grit, but who knows what. Even without the grit, the engine is worn out.

...that being said, the driver side valve cover has leaked pretty badly nearly the entire time I've owned it, so even though I've stayed on top of it pretty well, there have been instances where it's gotten low(er) on oil. Not enough to trip the light, but enough to start making the valvetrain noisy and get my attention.

 

I think the oil got contaminated with something, possibly before you got it..... Those are some pretty significant divots.

 

I did notice that the bottom of the oil pan had a fair bit of what felt like grease settled in it. Thick and sticky. It can't have been there long, because I had the pan off early this year or late last year to replace the rear main seal, and the pan was clean then.

Sounds crazy, but the only thing I can possibly think of that could have caused that is marvel mystery oil. On a whim while I was scratching my head and wondering if it had a stuck lifter (so it was already making the noise by then), I dumped some of that in the crankcase to see if it would free it up (not really expecting it to do anything, but who knows). Maybe it reacted with the additives in whatever oil I was running and caused it to gel like that.

No semblence of that grease-like substance on the rods, mains, etc...just in the bottom of the pan. None in the oil pickup.