Crankshaft Turning and Re-applying Nitride Coating

[OldSixBolt]

As many of you guys may know, our factory cranks come with a nitride hardness coating that gives our cranks their durability. However, with as many tore up cranks out there, it's beginning to become hard in some places to find a good condition unturned crank, especialy the six bolt stuff.

I know in the aviation industry it is common practice to have crankshafts cut and nitrided. From what I understand though, they have to heat the crank up untill it is red hot to apply this coating, which can somtimes warp the crank. From what I understand, they afterwards have to be installed on some special jig and be checked for straightness.

Has anybody had a crank re-nitrided on a 4G63 application? Is this a practical solution?

[Marco]

Yes I have done it on hard to find diesel 4G63 cranks, and yes they did have to be straightened. With a big brass hammer :)

[OldSixBolt]

Diesel 4G63 cranks? Bigger rod journals or somthing?

[1320Addict]

What could be better then a diesel 4G63? Its the best of both worlds.

[Marco]

There was a rare old 1.8L diesel 4G63 that had phenomenal 6 bolt cranks. The best part about them was the large radius fillets on all the journals.

[Aaron@English]

The 4D68 was available as a 7 bolt only though correct? I have a guy in Indonesia that I guess has talked to you before Marco, named Dixon. Really fast Evo 2 or 3. At any rate he said he would send me some 93mm cranks if I wanted them.

[aliquantus]

I cut one down and had it re-nitrided, just not worth it unless they all dry up used. It was about $350 all said and done, but that was 7-8 years ago.

[Marco]

You are talking about Dixon Chen. Get him over here on the board next time you talk to him. I've known that guy for years.

There were 2 4D68's a 93mm and an 88mm, both were 1.8's both had different size bores, the diesels came from the factory sleeved

[OldSixBolt]

How hard are these cranks to come across nowadays, Marco? Are they worth searching for over the standard USDM gasoline cranks?

[Marco]

I will probably never come across another one in my lifetime. Those cranks cost me 200 each to ship when the shipping was cheap. They came all the way from the far east.

For the money these days, its not even worth it, I just got quoted today, grinding and renitriding for a crankshaft. It was gonna cost me 550. For that price you should just buy a new crank. Plus for a little bit extra money you can get yourself into a nice aftermarket crank.

[The Wookie]

Been waiting 4 years for my 93mm diesel 7 bolt cranks.

Shoulda, coulda, woulda.

[KDeiwert]

I have had quite a bit of experience with Nitriding various engine parts in these 4G63 engines. Its important to remember that most nitriding processes involve high temperatures. It is possible to "undo" some factory heat treating while performing certain Nitriding processes. I have had a crank looked at by a metalurgical company near me and I saw that there was room for improvement as far as the depth of the factory nitriding.

With that said, I have had a few 6-bolt cranks salt-bath nitrided. The max temperature reached in that particular process is 1075ºF nominal.