This might be a dumb question, but... Can you use a good running motor to rebuild a locked up/bad motor? Basically, taking all the parts out of the good/rebuilt motor and dropping them into the bad motor (***uming machining work turns out OK). The reason I ask this is to keep the original block (and motor serial #) with a vehicle, instead of just dropping in the running motor. It would be cheaper than getting a rebuild kit, though I figure you'd have to replace some gaskets and bushings and such.
You could feasibly take the decent parts out of a good rebuilt motor, BUT, you'd want to go ahead and replace all the wear items any ways. Things like bearings, and rings, it would be wise to replace them all since you are already in there. Rings wear to match the conditions they were broke in under, so using them over isn't the best idea. Especially considering the cost to get new ones. Also, the "bad motor" you are speaking of would probably need machine work anyways, so, it wouldn't really make much sense to spend all the money on machine work, and then put used parts in it. Personally, one of my favorite things to do with a tired or worn out "numbers matching motor" is to replace it with a healthy engine, and then rebuild the original at your leisure. That means you'll have more time to hunt for deals on quality parts, and do a good job. Once I have the original rebuilt, I usually MARK THE BEJEEBUS OUT OF IT as to what it is, and what it goes to, clean it, use ***embly lube in all the important locations, plastic wrap it, and put it on the shelf.
Bodi makes a good point IF you have a car where "matching numbers" makes it valuable. I had a car with the original, matching #s engine that was a bit tired. I pulled it and put it on a stand and ran a more powerful engine when I drove it. This way I also preserved the original engine from stupidity on my part
As the previous gentleman suggested, I´d just swap in, run and have fun w/the "rebuilt" motor in the car while I took my time w/the "original" motor apart from the running car. -Less downtime, more simple from the machining -standpoint with matching amount of wear on the block&all its internals(?), plus in the end You´d end up with two complete engines as opposed to just one and a pile of "leftovers"...Just my 2c´s. Good luck.
It doesn't get around the need for oversize pistons and a rebore if the bores are worn Re-sleeving would be too costly. I've done what you suggest here but the opposite way, I went hunting for a block that would take my parts without needing a rebore
Basically you might save the cost of pistons. Right now you have 1 good engine and 1 bad engine. You could dis***emble the running engine to check bore size . You now have two non runners. Conceivably you could have the bad engine machined to accept running engines pistons. There's a large possibility that it is impossible to do this You still have 2 non runners. Lets say machine work goes well, you'll still need a master overhaul kit less pistons. plus machine work and ***embly. You still have only one running engine. Depends on why your block is locked up , but most of the time the rings seize to the cylinders. A careful dis***embly usually yields a machine able block, caps, rods, and crank leaving only new pistons being needed to accommodate the required over bore. You'll still need the master kit. Now you'll have 2 good engines. One of wich can be sold to offset the cost of the rebuild. Not that you couldn't sell the parts leftovers but a complete good running engine is more marketable.
Will haveing matching numbers on this particular car add any more value to it? If you are planing to keep it forever, is sombody really going to stick there nose in it to look at the numbers? If one is planing to sell it at a later time, offer the original engine as a bonus and let them deal with it.
You will ned to know what your trashed block is going to clean up at and then you will want to size the rebuilt motor to suit. It could be done depending on how much dumb luck you have.
Thanks for the info everyone. I ran across a supposedly-rebuilt motor for a decent price, except possibly having to ship it. I don't know how much value difference having the original motor in the vehicle would be, but if I keep a L6 it would be novel to keep it. I guess my big worry is that I was told years ago the vehicle was parked with a hell of a knock in the engine. I have a some amount of mechanical experience, but the only engines I've torn down are small engines, so I'm not sure how much damage could be in there. I guess I just need to tear that motor down and figure out what's wrong. Makes sense, and I agree it's still going to be a lot of new parts required. I guess the only saving grace is the possible need for a crank or rods from another engine. Since I don't have the other motor, it's probably not worth pursuing until I know what I'm in for.
A knock is going to pretty much guarantee you the crank needs machined. If a rod, they can be resized easily, if a main the block will usually need a little more work. Your machinist can answer better on that issue.
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