At PRI I talked to a Nitriding shop and was given the sales pitch particularly the zero effect on dimensions. They through out a $125 to Nitide a Crank. They stated they use a salt bath @ 1000F and stated the part (crankshaft) would be black and and ready for installation as returned. I have to wonder with the abundance of Chinese (hardening=LOL) based cranks and Factory Ford cranks in both steel and iron that have more then likely been turned beyond the factory hardening is this something that is missing?
On the other side I have to wonder about the potential for over hardening components such as Cams and Gears.

I can't speak on the new Chinese cranks, but I just had a 428CJ crank done by Moldex. My engine builder mentioned that 428 cranks are prone to cracking without it. I'll take their word for it.

the type of nitriding? Bath Gas etc

I really don't know the various types of nitriding. Mine was like a darkish grey color. It's in the engine now.

I don`t know at what stress level Moldex was talking about, but my stock factory 1U 428 crank has been working just fine in the Fairmont for the last 14 years with nothing more exotic than a simple .010-.010" cut and polish. Not to mention whatever life it had led before I got it. I had it magnafluxed last year, and it passed with flying colors. Hundreds of 6000 +RPM clutch drops and all.

428 powered Fairmont drag car, Best ET:10.03@132.11MPH, best 60 ft: 1.29
59 Meteor 2 dr. sedan 332, Ford O Matic
74 F350 ramp truck 390 4speed

Rory, I can't really say. Although, years ago I ran a 428 without any problems then took it apart and the crank had a hairline crack in it. I just went along with the advice for insurance.

I was under the impression that Ford used an alloy that was hard all the way through and did not need treatment like nitriding. I think this was discussed here some time in the past.

Nitriding will only harden to a specific depth, not thru and thru. I would think that in the case of a crank or cam that this process (thru and thru) would cause the cam or crank to be brittle and subject to failure.

Aerospace use of Nitriding is for hardening bearing surfaces or a part that will see some contact and needs a harder surface. Other then that a depth hardening would be used, ie heat treating to bring up the RC value.

Just what I remember that's all.

The only reason all cranks are not nitrided is cost. The process creates a thin layer of super hard, wear resistant surface on your crank journals. In many cases you can spin a bearing and have no damage to the journal whatsoever. You get the benefits of wear resistance combined with the toughness of the underlying material. The hard outer layer also inhibits crack initiation.

If you are suffering from insomnia, here's a good paper to read:
http://www.forging.org/FIERF/pdf/CrankshaftProjectReportIAug2007.pdf

From page 10 the paper:

"Fillet rolling and nitrided
samples both produced approximately a factor of 1.8 increase in fatigue limit when
compared to untreated samples."

I would consider nitriding a great choice for a serious crankshaft.

- Bill

The salt bath method of nitriding is the old school method. Most of your better known crank companys use the plasma ion nitride, witch is a gas,electric process in a vacuum chamber where the cranks stand up as opposed to laying down in a salt bath. Uses a lower heat and cranks are not black as a piece of coal when finished. Crank will have a ash color like a burnt piece of charcoal. On all my super stock 428 cranks I would follow up with a cryo process witch is a through and through treatment. Both processes are good for castiron and steel.

Thanks Jeff Colvert
former ACCUCRANK Custom Crankshafts, owner

Jeff Colvert
Jeff Colvert Racing CNC Cyl.Heads
69 Mustang SS/G first in the 9's
68 GT500KR 2330

I have used both nitriding and cryo-treat on my sports car race cranks, but not at the same time. Nitriding gives a good long wear life but cryo-treat not so much. While nitriding is very hard and wear resistant it has never proven to stand up to a spun bearing for me. Fortunately, I figured out how to get my bearings to survive before I used up all the availble cranks in the country.

Gary,SOCHBOB, My process was to finish grind crank and polish as I was going to run it.Then have it ion nitrided, then cryo treat,check for straitness, finish polish with belt and polish compound.Diameters varied very little. The cryo by it self would not save a oil problem only makes crank stronger to resist breakage. Still need the surface hardness of nitriding to prevent wear.

Hope this helps.

Jeff Colvert

Jeff Colvert Racing CNC Cyl.Heads

69 Mustang SS/G first in the 9's

68 GT500KR 2330

I had a 428 crank gas nitrided. The ginder told me that both cast and steel cranks would grow during this process and that they would have to be cut twice. Once to get it close prior to nitriding and once after to achieve final dimensions. Is this standard for this process ? He also stated the iron vs steel cranks would grow at different rates. What say you ??

Bob

06 Dodge Ram CTD
72 "Mach 1" V Drive 390
69 Mustang SCJ 10.86 121.83 1.494 60 ft.
65 Comet 428
53 Willy's P/U 390
32 Ford P/U
30 Ford Bantam project 427 Sohc

...the same nitrided 1UB crank has been in my Mustang's 454 incher since 1985. It's stood some actual drag racing (really!) with and without "squeeeze", lotsa street "encounters", and a WHOLE lota idle'n 'round town. Been out of the motor 4 or 5 times over the years, measured and magg'd, and put back in. Seems to work for me, and I had the 1U in my new blown deal done too.

suggested that his builder talked about cracks, and not Moldex. Moldex uses the gas, stand-the-cranks-on-end style of nitriding. I just had one done, including the enhanced fillet, etc. and, as said, it came out a dark grey color. That's except the journals, which are polished as the final step.

Several years ago I had Moldex do a 390 crank for me. It originated in a 330 PI engine. The engine suffered a catastrophic failure, including one broken rod and another damaged. The engine was turning 7500 RPM at the time and the destruction caused enough heat to warp the crank out of straight by .035. Although the journal was damaged severely, the crank held together.

I believe nitriding is worth the effort!

KS

Dimensional Changing the crank with Nitriding would be a hell of a stunt from what I understand. Since the changes are made on a molecular levil with heated gas atoms altering the structure that would be pretty cool to for anyone to even be able measure that minute a change.....however if due to heating (the guy I talked with mentioned 1000F max things got pliable and were distorted by wacking or dropping the crank dimensionally things could change big time but not the machine work dimensions..JMHO