searching for unicorn -- I mean machine shop

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unklpat
Roadster Fanatic
Posts: 239
Joined: Fri Feb 15, 2019 8:43 pm

Re: searching for unicorn -- I mean machine shop

Post by unklpat »

Jim, You've not given any details as to what the wear differences are, regarding nitride coating or not. From what I can ascertain, nitride coating is for "racing or other high speed operation". There are probably 10-15% of U20 cranks, or R16 cranks that can be standard, or .010. Are the rest junk, or need a $300 treatment before grinding? I'm not trying to pick on you, but you throw out terms, and statements. I'd just like to know where they come from. You have a lot of knowledge, and are a benefit to this forum, but I'm a guy that likes factual answers, and when someone dodges the questions, I tend to push. Please don't take it personally. Pat
JT68
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Joined: Sun Jan 27, 2013 9:43 am
Location: Cumming, GA

Re: searching for unicorn -- I mean machine shop

Post by JT68 »

Hi again Pat, no one is dodging any questions, NISSAN determined that hardening/gas nitriding was needed. I've said that before: Nissan cranks were forged and factory hardened. They are very high quality crankshafts. That's one of the reasons Nissan cranks held up so well compared to cheaper manufacturers and have such a good reputation for durable bottom ends. The factory forged cranks are very hard and strong. It makes a big difference and pro engine builders already know this.

It only becomes an issue when you cut away all the factory hardening which is good to about .015-.017" I've said this before too and told you the same thing on the phone a couple times now, right?

With .010 the hardening is still there, with .020 it is pretty much ground away. AS I said before, one more time, once the crank wears into to soft steel beneath the hardened surface, the cranks wear poorly. That is why Nissan hardened them in the first place! They were trying to build rugged and durable engines.

There are definitely still .std and .010 cranks around- I'm sure some guys right here on the forum have them.

Yes, most Datsun cranks are boat anchors once they are cut to .020 or beyond. In part that is because you have to nitride BEFORE turning, so if you don't do it BEFORE it is cut to .020, and then you harden it, you are going to .030. Most pro builders will say "you are really better of finding a better crank" at that point!

They also know that the difference between the hardened surface and the fairly soft core steel is about 50% bearing/crank life! Meaning the hardened crank will run about twice as long as a soft crank. And again, I did point out that it is often the thrust surface that fails on the roadster crank once you are through the hardening.

The specific knowledge came from decades of building roadster engines - literally. NOT just one or two engines! The hardness depths were determined years ago on race cranks in the 80's (specifically during Bob Studdard's D-prod engine program at Sunbelt).

My advice is simple and free, if you have to run .020, get it nitrided before it gets turned-and it will work fine for a long time.

If you have a non-nitrided crank at .020 or .030, you are really better off shopping around for another crank IF you want crank life and durability consistent with a Nissan factory crank. If not, it doesn't matter.

We are glad to help anyone out if we can. Thank you for calling today Pat, for the sake of the forum, it’s probably better if we talk real-time rather than going back and forth here. Thanks again.
LT/JT
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