Can anyone tell me if this is normal?

[PeteMelb]

Hi All, First a bit of background to assist: This motor was purchased from a chap that strips and parts out wrecked trucks, the motor was apparently rebuilt 400,000klm before it was wrecked, at first the story was the truck twisted the frame but later he found out it was rolled so the motor may have been running on its side or upside down who knows. Anyway when it was fitted into another vehicle and started it had one hell of a knock that sounded like a gudgeon knock. but the individual that sold it to this man has pretty much wiped his hands of it so he's now come to me for help, I started it and its got a knock alright that I'm now looking into.

I have just unbuttoned the bottom end of this ISX motor and the crank journals and bearings look in excellent condition, except for the blue discolouration on the crank (photos below) something I've not seen before and wondering if its from manufacturing or if its been cooked, I would assume if it was cooked then the colouration would not be as even as these seem and the journals would be stuffed but the mains and big end bearings I dropped so far have No wear AT ALL on them and that makes me suspicious if its supposed to have done 400,000 I'd expect some wear but they look brand new, the journals themselves look blue in the photos but they are not they look perfect to the naked eye no colouring at all. the conrods have no discolouration and so far look fine so I don't think they were cooked.

Bottom line is, If the discolouration is normal then we can proceed with just locating the knock and fix that issue, but if you guys think its been cooked then I may have to break the bad news to him that its gotta come out again, I'd appreciate any advise I can get on this crank.