Grinding nitrided 2000 crankshaft - the ultimate sin or necessary evil?

[aussieneil]

Now that my car's overlength steering column issue has been dealt with (thanks for the input and guidance!), my next attention turns to the engine.

My car had been laid up for 26 years. The story was that the then owner had sent a lot of money on the engine, but then the head gasket failed, and he simply lost faith in the car, cut his losses, and purchased a 5 year old Alfetta GTV 2 litre, pushing the '72 coupe into the back of the family's shed at Yarrawonga.

Stripping the engine seems to confirm that story. Two pistons was totally rusted in their liners, and there were copious quantities of the most amazing oil/water emulsion I'd ever experienced in the sump and radiator. By removing the sump I was able to unbolt the big end caps and individually extract the pistons and liners, and then cut the rusted-on liners from the pistons so the con rods could be extracted.

Apart from the 26 year reaction between the oil and coolant, the other thing that struck me was that the pistons, liners, and big end and main bearing shells displayed almost no wear at all, probably not even run-in, and the crankshaft journals were perfect, as if they'd just been machined and polished yesterday.

But the big end and main bearing shells are clearly marked as being 0.010" undersize, and the conventional wisdom regarding 2 litre cranks is that they are nitrided and should not be reground.

Obviously I can't ungrind the crank, and doubtless it needed it back in 1989 or 1990 when it was done.

What experience or wisdom can other owners offer? Is the .005" cut necessary to decrease the journal diameters by .010" deep enough to completely remove the layer hardened by the factory nitriding process? Will the crankshaft be fine with non-competiton use and regular oil and filter changes, or is it doomed?

[jazig.k]

Nitrating, typically treated by rule of thumb, to a depth of .010". That's the modern process anyway. No idea what the bean counters were doing in the Alfa offices...

[LaStregaNera]

My first (Alfetta) GTV had the crank ground and re-nitrided as part of an engine rebuild - commonly done.

Nitriding thickness can be between 0.2mm and 1.5mm - the depth is related to process time, so I'd suspect that the Alfa cranks are on the shorter process duration side of that.
It may have been re-nitrided when it was machined - either way, if it's in good shape now, it'll likely be fine.