Do you have the Iron Duke, or the AMC 150?? Sometimes people didn't know AMC had a 2.5.
Sounds like you have a spun bearing on the crank. Mine went out last winter. The engine doesn't cease up right away when it's spun on the crank or the rod bearing. It's when you continue to run it for awhile. That's when oil stops getting to the cylinder cooling shafts and the whole thing heats up to warp out of shape and then you're SNAFU.
The same thing happened -- the rapping, but still running, and oil pressure drop. I just have the "idiot light" dash, so when that light came on and I lost some power I was 40 miles from home thinking "Can I make it??" I did, but worried that my engine was done with. I found by varying my rpms, the light would go on and off. I'd start slow and gradually run higher and higher. Every ten minutes I'd have to turn it off. But I got it home.
My AMC 150 had 356K in the MJ when everything just finally wore to nothing. I pulled it apart to find that the 4th crank bearing had spun, and the other weren't too far behind. Had it rebuilt, but the rod bearings looked like they were better than the crank's, so I'm guessing your crank has spun.
Bob, I've never seen that, but I'm sure it's possible. My bearing halves just spun about 10 degrees since the little teeth were worn flat. The porthole for the oil that used to line up with the hole in the crankcase was shut off so no oil was in that cylinder.
I got 40 more miles out of mine. The block was rebuildable -- and I did have that done. I don't know how much more I'd run yours. The 4.3 is so tempting . . .
See Jayme ASAP
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