Crankshaft: What to do? Nitride Coating, Machine Work, Prevention

watsonlk

Registered User
I've searched several threads but looking for any new info.

I just broke an Atlanta Crankshaft at less than 10k on a totally new\machined short block.

I am putting trying to re-use the crank that came out originally but it spun the all too familiar #2 and grooved the journal.

So... Any thoughts on these?
1) To make the crank as bullet proof as possible what machine work and prevention could be taken.
Obviously restricting any turn to one pass, polish where possible.
I've read about NITRIDE coating on crankshafts while flying planes, but don't know much about it other than it is praised to lengthen the over-all life of the crank.

2) Magnaflux, if so how high can you go on the amperage? I've never performed it but have been told the higher you go, the more definitive the test will be, but too high and the steel is weakened.

3) Balancing or chamfering the oil passages?

4) I have a new HB but it's a stock one in with less than 12k on it.

5) Sacrificing a small gerbil, or anything else no matter what.

I didn't have any detonation and running perfect, snapped at 1800 rpm, 3rd gear, 35 mph no load.
I just don't see how it busted smooth after rod journal 1, and trying to prevent having to do it again.


I have a few mods with the biggest adder being a 75mm BKK TB.
I'm not looking to ever push more than 275-300 if that much, but want it to last longer than before :mad:

Thanks
 
Chances are the grinder on your previous crank screwed up the radii on the rod journal. This is the #1 problem.

The SC crank does not have an undercut on the radius so it is critical that the grinder duplicate the OE radius when grinding. This is the #1 problem/challenge when grinding the crank.

Then the #2 problem is balance. Don't skimp on the balancer, get a BHJ. Then, balancing the Ford 3.8L crankshaft correctly is another bit of an art. Due to it's split journal design, it is necessary to have more than just a rudimentary knowledge of balancing to get it right.

I spend a lot of money for a good balance and crank finishing job. Beyond that, the rest is just gravy.
 
Thanks Dave, you might have talked to my friend\mentor Russ down here around Dallas.

He has gone big time compared to my goal, stud girdle, H beam, who knows what machine work.

The guy that did his work seems to be one of the premier builders around here that has months wait time before race season.

He has a full machine shop with aluminum Outlaw motors laying around, which knowing plenty about myself, proves he should know a little, I hope.

Big money in his equipment and work on hand that I think his track record is good.

I will pass this along when I talk to him about the condition of my #2 journal.

I'm hoping the guys at Atlanta Crankshaft just messed the reman up.


Do you have your cranks magna-fluxed for cracks, does that prove worth the cost and add any security of the crank in question? I doubt this was done by AC guys.

On another topic, I Plasti-Guaged my new bearings and at 10k miles the things are worn to, not thru the brass layer just about a pencil eraser size in the center of the curve.

Any reason to be concerned do you think?
 
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The motor had insufficient clearance in the first place, hence the worn bearings. Also, going to an aftermarket rod allows you to use an HP bearing instead of the stock SC bearing which will help. Detonation also wears bearings prematurely.

Grinding the correct radius on the rod journals is a PITA and most shops don't want to do it because they have to make a custom stone just to do the job right and then they will never use that stone again unless they do another SC. Standard 3.8's are undercut and don't require the same setup. Same goes for balancing. You have to make custom bob weights because standard weights don't physically fit.
 
Well I see why you get a lot of 'what would you do Dave?' posts.

I didn't realize the radius was so hard to deal with, not much mention of it from what I found, but makes perfect sense.

Likewise, since it's motor specific, the machine shop didn't use a block plate to bore my holes and I'm hoping that isn't an issue somehow.

I will take your advice and see if I can find one around here that knows what you're talking about.
I'll ask my friend but I think his 'new' crank only needed a polish so it wouldn't have been an issue for him.

I'm also wondering on the MagnFlux, do you have any experience with doing that and has it benefited or missed any flaws that you've heard of on ours?

Thanks again Dave.
 
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Magnafluxing is a cheap way to scope out some cracks. More importantly, I would check the crank for straightness. How did the main bearings/journals look? I have seen bearings eaten up by incorrect finishes on the journals almost as often as the wrong clearances.

Any true high performance shop should have the correct stones. Also, those shops will normally chamfer the oil passages on the journal whenever they resurface the crank.

HD bearings are made up of less material and is a harder composition of bearing. You're better off staying with Clevite, which has thicker layer of babbit.

The best bearings you can get are KING bearings. I'm not sure if they make them for 351W, but I don't see why they wouldn't.
 
Try contacting Crankshaft Specialists in Memphis. They can hardchrome the rod journals and return them to original specs. I had one done a couple of years ago that I haven't used yet. They told me it has a Rockwell hardness rating of 63 and is better than when new. It might be a little bit pricey at $550, though. You could always try to find a good used unturned crank in the classified forum.
 
Dave,

What brand bearings do you use ?

David

I used Clevite bearings, and did the plasti-guage since I've built quite a few motors I think I had the clearance OK.

The main bearings look good, except some blue from heat on the #2 which is probably from when the crank was about to snap. Not bad but any isn't good.

I'm trying to find an untouched crank and go with a polish only since Dave pointed out the radius issues with turing.

Thanks guy
 
Try contacting Crankshaft Specialists in Memphis. ...

I Googled them and the first three entries that came up were complaints and stories of total screw job that lasted a month long.

I need a quick turn-around time and quality work.
Maybe this was a deal that isn't described, always two sides, but I can't chance it.

Thanks for the tip though.
 
Try contacting Crankshaft Specialists in Memphis. They can hardchrome the rod journals and return them to original specs. I had one done a couple of years ago that I haven't used yet. They told me it has a Rockwell hardness rating of 63 and is better than when new. It might be a little bit pricey at $550, though. You could always try to find a good used unturned crank in the classified forum.

Doug at Crankshaft Specialist has a HORRIBLE reputation. If you keep digging, you will find the countless number of people he has screwed over. Mike, if you have had good dealings with him, I honor that and consider you one of the lucky ones. Everyone else better think twice....
 
Yeah, he was always nice to me, easy to deal with, and was very prompt. He even gave me a better deal when I asked if he could lower the price a little. Now I'm leary of this crank I had done. I hope it's good. The crank itself looks beautiful. Of course I haven't run it yet but I was going to send it down to a place in Daytona Beach and have it Mikronite treated before installing it in my new motor. I think I'll take it over to a local engine shop I deal with here and have them check it and mic it for me before I do anything with it.
 
Couldn't hurt to have it double checked...thats for sure. I'm sure the guy is capable of doing good work. The question is, did he??
 
Right and since it's going in a high HP motor I don't want to have to worry if it'll break. The original damage was only .005. He said he took them all down to .005 and hard chromed them back up and machined them to original specs. The plating process is done at about 260 degrees. Like I said, it looks beautiful. I've got another crank I need to have evaluated so I'll take them both over to the engine shop and have them both checked. Hopefully they'll be able to verify the radiusing is correct.

Upon further googling, it appears this guy's out of business.
 
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MikroNite sounds similar to shot peening rods.

It uses an abrasive material to pound the metal making it denser/stronger I'm assuming.

Need to check the cost on that but wondering if need it for max 300 hp motor.
Daily driver, occasional AutoX.

Checked Crane Cams website and they do in-house MickroNite, $500 for a crankshaft. OUCH!!

Found this interesting:
...the surface of the crankshaft confiscated out of the Erion Honda was highly polished. And for some reason, that if a finger was used to swipe a line in the oil film coating that crankshaft, oil immediately flowed from adjacent parts to recoat and re-establish a continuous oil film.

...during the post-race tech inspection. The photo showed the crankshaft to be very shiny and polished; it did not have a stock crankshaft’s dull surface.

The source offered his opinion that the crankshaft had been surfaced-treated in a tumbler full of some sort of polishing medium, to reduce friction.

http://www.roadracingworld.com/news/article/?article=32028
 
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to the OP

your confusing magnafluxing with mag particle. Magnafluxing is spraying it with a red dye and after it dries spraying it with a developer to see if it has any cracks.

mag particle is using an electromagnet and an aerosol spray with magnetic metallic shavings to draw the particles to a crack that may be up to 30 mils below surface.

i am a refinery inspector and do both mag particle and magnaflux. I also do ultrasonic testing (mic'ing) and x-rays.

However, with mag particle turning up the power only makes the magnet burn up faster. It won't cause it to find cracks any deeper. They usually all only have 1 setting.

so short answer is no, turning up the juice on the mag won't make it find more cracks.
 
Dye Pen vs. Magnaflux & Magnetic Particle Inspection

The use of visible dyes alone to check for cracks is known as 'dye pen' or 'Dye Penetrant Inspection'. A non-drying red penetrating dye is applied to the suspect area, which is then cleaned with solvent (leaving dye in the cracks), and then bathed with a white developer. Any remaining red dye contrasted against white developer marks the crack. There is a black-light/non-developer variation on this method. No magnets/electricity involved.

-=-=-=-

Magnafluxing/mag-particle checking involves the use of magnets/electro-magnetism (field flux) along with iron dust/particles (less dust where cracks have weaker/fragmented fields) and can include the use of ultraviolet light & various dyes/carriers.
 
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Thanks guys, never searched it out but knew some that have paid to have it done.

I think I'll read up on it a little more.
 
Mike, a visual inspection should tell you if the rod journal radii are still there and still smooth. That will tell you most of the story right there. Now, if there are subtle dimensional problems, as posted in one of those horror stories found through Google, that would be harder to check. (One poster said the crank throws were all different lengths. That would be a nightmare, trying to figure out why one cylinder keeps detonating!)
 
Mine was done in '04 which was before all this stuff happened so mine's probably Ok. It appears that the guy developed a white powder problem and started feeding his habit with customer's money according to some of the posts I read. I'll definitely have it checked out though.
 
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