Engine replacement

[Subzilla]

Finally tore down the "broken crankshaft" engine on the Sub in the last few weeks. The crank is in 2 pieces between the back 2 connecting rods and the front 6 (not familiar enough with the technical terms to describe exact location - I will post picture).

Now the long story with questions: I acquired 2 rebuilt engines about 5 years ago from a friend who got them from a friend who got them from a shop that contract rebuilt 6.2/6.5's for the military. These were extras they had when the contract ended. They were dyno-ed and checked out good by the shop when rebuilt. I planned to put one of these in the Sub but I've had always had a fear that this shop maybe just made them "good enough" until the next rebuild.

Took the heads off the rebuilt engine and found semi heavy surface rust on the front 2 cylinder walls. These sat around for a few years prior to my ownership so I'm not sure when water got in. Been in my garage for the last 5 years.

One of the piston tops has rust and it appears to extend into the rings. Is this usable with some minor touch up?

Some other things that confirmed my lack of faith in the shop:
1) push rods were installed with copper ends up and down!
2) one of the head bolts was not torqued as well as the others.
3) cylinder walls appear to be vertically scored with no hone marks. I'm thinking this is not the best thing? Not sure how much the military abused these engines.

Would another option be to swap crankshafts to the broken engine? Could/should I do this without removing the heads or replacing piston rings? I replaced the heads 35k miles ago and the engine has 340k miles with no prior rebuild.

[DmaxMaverick]

If the block isn't cracked, I'd be inclined to just replace the crank. Unless there was another reason, you'd be money/time ahead. From the sounds of it, what you have (once the crank is replaced) is as good or better than what you'd replace it with. A complete rebuild is almost always ideal, but I don't think, in this case, you will gain anything doing it. Don't fix what isn't broke!

[Subzilla]

Reinspected my original block closer and find some bad news. The web at bearing cap #4 is severely cracked which is where the crankshaft broke. Anybody need a boat anchor?

Guess I might throw replacement engine #2 on the stand and see what the insides look like.

[Subzilla]

OK, after playing musical chairs with engines and getting the 2nd reman on the stand, I popped off the heads. No rust except for one cylinder that has some surface rust spots, probably due our Southern humidity.

What is the best way to remove these 3 spots of rust inside the cylinder? Thought about emery cloth but don't want stuff falling down with the rings.

Also, I can see the rebuilder's cross-hatching in the cylinders although they seem a little flatter than 45 degrees. A few of the cylinders have some cross-hatching rubbed off just in vertical patches toward the outside of the block. I can't imagine this to be a good thing??? Can it?? This engine was supposedly dynoed after rebuilding but not run in anything.

[DmaxMaverick]

If the engine is out and on a stand, might as well pull the rotating assy and run a bottle brush through the cylinders. It'll either clean up the rust, or show it needs a bore. It will also give you an opportunity to check the conditions of the rings, wrists and skirts. Minor surface rust, if it's negligible, can be cleaned up with Scotch-Brite. If it needs much more than that, it isn't minor.