John Deere 1650 engine question

[golfcartman]

I have a good friend that has a 1650. A while back he noticed the engine making a knocking noise. He shut it down quickly and hasnt done anything with it
Til a few days ago. They broke it in half and found the crankshaft would move up and down. The rear main bearing bolts had backed out and letting it move
Up and down.
Has anyone here ever seen this happen. He wanted me to ask if anyone else ever saw this before. Thanks for any info.

 

[used red MN]

Sorry, but I have no experience with that model and of course have never seen main bolts back out. I will go back to something I always say; nothing made by man is perfect, any form of breakdown known or unknown can and will happen. In the first repair shop I worked in out of high school a local young farmer who was several years older than me brought his 78 GMC with a 400 engine in for an overhaul. He mentioned that occasionally he thought the engine ticked a little more than normal. I cannot remember the order in which we discovered the two unusual problems with his engine. On a Chevy/GM small block the rocker arms pivot on a half-hemispherical part about 1/4 inch thick and 3/4 inch in diameter with a 3/8 inch hole to mount on a stud, see linked example. One problem it had was an extra one of these had been floating around on top of the intake valves for quite some time. In fact long enough to nearly wear through the intake valve port into the water jacket. I believe it had evidence of it having been on top of only 2 valves. No guarantees how long it had been in there it may have gotten in there at the factory, but it may have gotten in there during a repair. However, he had not had any work done on it while he owned it and I remember seeing it around town and it was a nice looking lower mile truck when he got it. The second unusual problem it had was definitely from the factory. One head bolt near the center of the head had no hex on the head it was just round. The mechanical item that torqued the head at the factory got it screwed down to within a 1/4 inch of seated. Apparently GM used good sealer because there was no sign of coolant leak-by and all SBC head bolt save a couple have open threads into the block water jacket. That bolt was a show and tell item for years by the cash register of that business.
SBC rocker pivot

 

[golfcartman]

Wow, you never know what you might see for sure. I guess his main concern is if something else caused this to happen that they cant see.

 

[Fixingfarmer]

Improperly torqued while doing an inframe? Have had nightmares that something like that happened to one of the C15s we would do in teams while I was on the night shift for a cat dealer. Im not sure what that would do to the threads into the block but I dont know if Id be able to sleep very well reusing the block no matter how clean the threads were...crank would need attention. Possible line boring of mains. Potential for some chafing on the connecting rods and their journals...junkyard runner sounds like what Id be thinking about