Yes many of the cranks are cracked for example we have around 30 in stock, (threw a lot away when we moved int our big unit) and out of the 30 which remain I have around 4 which are crack free and do not need grinding, the rest all need to go to my engineer to be ground to see if cracks extend beyond nitride surface and if so then many of those are scrap too as I would not dream of using one in any of our engine builds.
And as you were correctly informed, the nitride surface goes down to around 0.25-0.30 on some and that's why its not a good idea to grind cranks any further than .25 as your getting close to the edge of that protective hardened surface which is very important on a turbo charged engine due to extreme loading the crank big end journals are under. if engine is na or fitted with a supercharger then the power delivery is much more linear throughout the rev range (no sudden force) so you have more leeway with regard to grinds.
Main journals are under just rotational force so you can get away with a lot more on those but generally if the shaft is cracked and it extends beyond a .25 grind (bigend journal) then its basically scrap
I will put up a photo etc tomorrow 'if I get time' of something you will find pretty astonishing and its a credit to just how strong these crankshafts and stock rods are
certainly surprised me.
And in answer to your question mr cosmic.........yes think I may have one in good order if needed, replied in your thread.
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