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I think Spockster is correct in thinking you may need a different crankcase half (or take yours have it welded oversize and machined down = $ costly). I was pretty sure the crankcase bearing is pressed into the case and then honed to fit. Why is/was the bearing seized to the crank? (You need to check the crankshaft to see if it is still perfectly round after having the bearing seize since that may have contributed to the event.) A lot of guys loose rod bearings but spinning a crank bearing would seem to indicate a specific lack of oil to that bearing. Especially if the other bearings are good.

I do virtually everything I can as far as overhauling my vehicles, but fitting the crank, crankcase and new bearings would seem to require better tools and skills than I have now. I could press in the bearing and even hone it to fit the crank but I no longer have the precise equipment needed to measure the ID of the bearing and the od of the crank with the precision needed. No way to use plastigauge here. I would not trust a Harbor Freight micrometer either and unless you are experienced at measuring with a inside mic it is real easy to get it wrong. If you do have quality micometers and are familiar with their use you are probably alright to do this but why it happened will need to be sorted out. Good luck.
 

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I think the crankshaft main bearings get their oil through the crankshaft so any blockage that stopped the oil from getting to the right side could have caused the failure if it is starvation that is the cause.. In reading my Clymer's I see that it sets forth the main bearings are to be pressed in and out with a hydraulic press. Since it does not instruct one to be aware of the alignment of any oiling holes I think they are oiled just like the rod bearings. Of course there could be grooves all around the backside of the bearing that provides the oil. I have a Ford Cleveland that has camshaft bearings available like that.

It then goes on the discuss how all the other bearings that are held in place with retainers can be replaced by heating the case in a oven and freezing the bearings in a freezer then driving then in place by hand (along with Red Locktite). If the prior owner replaced the mains in the case using this method, after driving them out by hand, they would eventually spin. That would account for the fact you do not see the heat damage usually seen when a bearing goes out like you describe. Also the lack of scoring on the crankcase between the bearing and the crankcase.

I recall from tearing down my son's engine the tabs on the oil tubes looked to soldered in place. That could be the "silver" look you are seeing. His is a 2005 and I would guess they might have used different material for the oil tubes over the years the more brass in the tubes the less likely they would be to break from vibration compared to high steel content tubes.

Since you mentioned your prior motor also had "issues" what kind of oil do you use, if you don't mind my asking?
 
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