Ford 172 Diesel Crankshaft grinding

I have heard that the diesel crank can't be ground, it just has to be replaces. Is there any truth to this? If anyone has had a diesel crank ground how well did it work?
 
Its not recommended to be ground undersize because those cranks need every gram of metal they can get! Ground cranks are slightly less noisy when they break (As the Psalmist says: "less metal to break = less noise it doth make") but most folks' hearing isn't good enough to detect it over the normal engine racket.
 
BUT- You can get bearings up to .040 undersize for both rods & mains, and All States Ag sells reground cranks for 350.oo with a 2 year warranty - for an extra 35.oo...
 
The tractor is a 981, the bad bearing is #4. What are my risks by grinding the crank? The crank breaking and having to tear it down again? Does their warranty cover any additional damage to the engine that their reground crank might cause by breaking?
cvphoto70833.jpg
 
I know of at least a half dozen 172 diesels in my area that are running with reground cranks. I have also replaced some that have broken that were never reground. Roll the dice.
 
So you are saying that if I rebuild with this crank it will break. So I guess my next question is does anyone have a good crank?
 
I would get it welded up and taken back down to standard. I do not know if either operation makes it more vulnerable to breaking. I do wonder if cryo treating the parts would relieve the stress and make them less prone to breaking.
 
Early Ford diesels were not to have cranks reground per the service manual, but I know some were done around here with no trouble. The 6000 Commander diesel I tractor drive with is .010/.010 and I have my fingers crossed, but it doesn't work hard anymore. I took three engines apart looking for the best parts to be used, and one of those had a crank that was already .020 under on the mains and standard size on rods. I think the journal fillet area is critical to prevent crank breaking.
 
I am never going to use this tractor for plowing, the most work it will do will be running a finish mower and a backblade. If the crank is still straight and none of the other journals have problems how likely is it to break?
 
Your crank has gotten hot on that journal, it is junk. Turning them from wear is a different story.
 
I have a 4000 4 cyl that I was using with a NH 489 haybine. I was mowing along just fine and the tractor kept gradually slowing down, I looked back and my windrows and cutterbar were clean. I am guessing it was 30-60 seconds and I looked down at the gauges and saw 0 oil pressure. Instead of just shutting it down I pushed in the clutch and it sounded like a machine gun going off. Shut her down and my father pulled me in to the shop. I pulled the pan and had one bad journal that i could see right away, I think #1. I told my father I was going to emery cloth it and put in new shells. You coudn'nt hear any knocking until I took the load off the engine by clutching. This journal was beaten so bad that it was totally black but actually polished up pretty good. It had beaten the insert almost all the way through to the rod,and it was paper thin on each side of the rod where it was hammered out. I put in new bearings without putting a mic on it and went back to mowing. The tractor ran well for a long time after that with no problems. I still can hardly believe the beating it took. It never broke. They are tough cranks. You have to decide for yourself but I have seen plenty of them turned 10 and 20.
 
I never understood why the no grind on those but doubt that it has to do with strength.
Rod journal diameter on that engine is 2.2985
Grinding it .010 would leave you with 2.2975
My wife was the math major not me but she's sleeping so I found an online % calculator.
Feel free to check the math yourself but I get this:
A .010 grind would leave you with 99.96% of the diameter it was before.
(A .020 grind leaves you 99.91%)
So I doubt that strength is a factor.
I would think it far more critical to maintain the correct radius on the ends of the journal. If it was my engine I would probably have it ground - by a shop that knows about that radius.
Online calculator
 
I wonder if the reason Ford does not want re-grinding is due to the heat treat process used? Nitride and Tuffride heat treated cranks have different depths of hardness. When I had the 6000 Commander diesel crank repaired last year it was straightened first, then re-ground .010/.010 and looks good as new. I did notice on all three engines I took apart, the mains had more were than the rod journals did. Standard size rod bearings would have worked fine, but all main journals needs attention.
 
Rod journal diameter on that engine is 2.2985
Grinding it .010 would leave you with 2.2975

Doesn't 2.2985 - .010 = 2.2885?

That would would leave you with 99.564% instead of the 99.96% that you said, but still a very high percent. I don't think that it is the amount of material lost, but the loss of the tempering, which is almost all on the very surface of the metal.
 
Not sure about the design of the 172 diesel crankshaft but some crankshafts cannot be reground due to rolled fillets on some or all journals which are removed when grinding undersize. 231 Buick V6 engines with turbo as well as 252 Buick V6 engines are so made.

Removing the rolled fillets weakens the crankshaft leading to early failure.

Dean
 
That's why I suggested you check my math :)

I don't know what Ford recommended back in
the day.
Don't know if they hardened those journals
somehow.
I worked as a welder in a big automotive
machine shop for about a year.
They had a a specialized, automated crank
welding machine there that I was shown how
to use and welded up maybe a dozen
crankshafts.
I welded a few Cummins, Detroit and even a
Straight 8 Packard crank once.
After cooling overnight I brought them
straight to the crank grind man.
I can not say positively - grind shop was
on the other end of the building - but am
pretty sure
when he was done they were done ie, no
hardening process was performed on them.
I am by no means an expert on this.
Just a bit of history.
 


Regrinding diesel cranks comes up here every now and then. I believe that the general consensus is that yes, they were not supposed to be reground, but that a little won't hurt. I agree with rustred that the journal is damaged from overheating and that it would take an aggressive grind to smooth it out. Maybe give yourself a few weeks of searching for a replacement
 
I don't have the time or money right now to get the engine apart and the crank ground anyway. Hopefully I will get it stripped down in the
next month or 2 and then see what the machine shop says.
 
As Dean says, no coverage for collateral damage, and you can usually count on some... That is some clean oil(for a diesel) on those cam lobes!
 
The oil wasn't that dirty and didn't appear to have any metal in it. It was diluted with diesel though so when I have the engine apart I will reseal the injection pump.
 
If the oil was diluted with Diesel make sure and check the needle bearings on the counter balancer!! I picked up an 861 that the balancer bearings went out on due to the crankcase oil filling with diesel 4 different times and it being run..
 
(quoted from post at 18:53:32 01/11/21) If the oil was diluted with Diesel make sure and check the needle bearings on the counter balancer!! I picked up an 861 that the balancer bearings went out on due to the crankcase oil filling with diesel 4 different times and it being run..

Robert, I went back to look at the cam. I agree it is unusually clean. Then I noticed something else in the pic that could be an indicator of a cause of the rough journal.
 
I bet they are out. When I got it I ran it for less than a minute because I was told it had a knock. I didn't hear a knock, just a loud squealing similar to a belt problem. I removed all the belts and it still squealed so I bet the bearings are out and that is what is causing the noise.
 
You can grind to .020 if I remember correctly. Running one in my 172 diesel. Definitely not any more as the crankshaft is heat treated.

Vito
 
Number 4 is probably easeist to break as power is added from number 1 to 2 to 3 to 4. I don't know but number 4 might be where they all break. Rear main also has load from flywheel.
 
Hello Tucker , The 172 diesel cranks can be turned but they have a Tufftride coating on them when new it is generally .027-.030 thick . I prefer to go .010 on mains and rods for a tractor that will be worked hard like they were when new , .020 is the max I go for tractor with a little easier life . Your crank is junk look for a good used one that is still standard size . These engines require a very complete and specific rebuild process to do it right if you want it to live a long life . I have rebuilt close to 1000 of these diesels over the years plus as many gas engines . If you go the cheap route I can guarantee it will not last 200 hours , if you spend the time and money the first time you better off . If want you can ask Vito one of the posts here he will explain the do It twice method as I did his engine after a cheap rebuild and broke a crank 150 hours later . These engines are 60 plus years old and not like the diesels of today . Do it right or don’t do it all . Tony
 

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