Broken Crankshaft Count?

Please pick the one that you had break

  • Total voters
    185
delong_1

delong_1

<< my work
Dec 5, 2008
1,282
0
0
38
Arvada, CO
motoking_1990 said:
I was wondering if anyone had been using a girdle or not. You would think tying the main caps and oil pan rail together would stiffen the whole thing up quite a bit. A girdle distributes the load throughout the block instead of letting it concentrate on the individual main webs. When I finally do my engine build a 14mm girdle, Xxl studs, billet caps, and new balanced crank are gonna be a must. I know a lot of these cranks have been on stock trucks but the built motors are what I don't understand. Not replacing the crank and reinforcing it someway under high hp doesn't make sense to me I understand money is a big factor but why not beef up the most important part. (That would be like rebuilding a trans and not replacing a couple clutches just because they don't look that bad.) :roflmao: If your going to rebuild something might as well freshen it all up. You don't want to have to tear it all back apart cause you didn't take extra precautions before. I would understand if it's all up to spec but why risk such an important part.

I also agree that regular maintenance needs to be done also. Once oil has done gotten hot too many times it oxidates, breaks down and then becomes acidic. doesn't matter if it is the best oil money can buy. But that's my opinion.
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i understand your thoughts but fwiw, my motor had my original crank, billet main caps, girdle, half fill on the block, studs, etc. i had about 3 oil changes on the motor, it lasted about 3400 miles and just a handful of passes.
 
Kartmnn

Kartmnn

New member
Oct 27, 2011
244
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0
East Providence RI
Are these motors that fragile? Any warnings? I need this truck to last awhile to pay off my debt and it makes the money to do that. Is it wrong I still trust a gas motor more?
 
J

jkholder09

New member
Jan 8, 2012
1,188
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Maryland
The engines are really great. The broken cranks seem fairly evenly dispersed between lly lmm lbz, and some lb7.
Stabilizing the crank to reduce flex with a girdle, billet main caps and studs, and replacing the stock balancer are the best and really only solutions that I could suggest.
I think some vendors offer a billet crankshaft if you want to stroke the engine.
The lml had a bulletin for the strange tick and supposedly synthetic oil cured it. (maybe less foam?) The lml block also has increased webbing but the main bearing area is different and therefore the lml blocks require an lml crank, the lml crank will accept the older style rods though.

Biggest question I have is whether or not an internal balance job would help with the problem. The lly balancer's have about 440 grams of weight slinging around and the cranks are breaking close to the front.
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
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Wyoming
jkholder09 said:
The lml block also has increased webbing but the main bearing area is different and therefore the lml blocks require an lml crank, the lml crank will accept the older style rods though.
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oh really...?


jkholder09 said:
Biggest question I have is whether or not an internal balance job would help with the problem. The lly balancer's have about 440 grams of weight slinging around and the cranks are breaking close to the front.
Click to expand...

all duramax balancers weigh more than 440 grams, Ill tell ya that right now.
 
juddski88

juddski88

Freedom Diesel
Jul 1, 2008
4,655
120
63
Chesterfield, Mass.
To run the crank itself, physically, nothing at all. to run the LML oil pump.....that's different. you either need the LML drive gear or shim the older one like I did.
 
J

jkholder09

New member
Jan 8, 2012
1,188
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0
Maryland
duratothemax said:
oh really...?

yeah the part numbers for the main bearings are different on the lml.
I was looking into building one, but the rod bearings initially were the same then they went to a second design and the tabs that lock them into the rods have changed design. The actual rod bearing diminesions are still the same. So in theory carillo rods could be used on an lml crank/block combo and be fine. The problem with using lml pistons is that the carillo rods have to be cut down at the piston area because the pistons have a much wider pin area.
I think this is to solve the piston cracking problem sort of the same theory of the oval fingers pistons.
I think fingers may have beat gm to the solution on this one though lol:thumb:


all duramax balancers weigh more than 440 grams, Ill tell ya that right now.
Click to expand...

I know the lbz/lmm actual have more weight than the lly/lb7 dampner, The last engine I did I used an lly dampner on an lmm crank.
I did get it balanced of coarse.
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
0
Wyoming
jkholder09 said:
ok ok 440 grams man sh%t my fault:confused:
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well someone might take your post as the gospel, and then go tell 10 of his friends, and then you've got 12 people telling everyone else that a duramax balancer weighs 440 grams...... this is why misinformation posted on the forums is frustrating and counter productive.

Im not going to get into this with you all over again, we dont need another counter-productive thread like the TCM tuning thread over on duramax forum..............
 
J

jkholder09

New member
Jan 8, 2012
1,188
0
0
Maryland
jkholder09 said:
The engines are really great. The broken cranks seem fairly evenly dispersed between lly lmm lbz, and some lb7.
Stabilizing the crank to reduce flex with a girdle, billet main caps and studs, and replacing the stock balancer are the best and really only solutions that I could suggest.
I think some vendors offer a billet crankshaft if you want to stroke the engine.
The lml had a bulletin for the strange tick and supposedly synthetic oil cured it. (maybe less foam?) The lml block also has increased webbing but the main bearing area is different and therefore the lml blocks require an lml crank, the lml crank will accept the older style rods though.

Biggest question I have is whether or not an internal balance job would help with the problem. The lly balancer's have about 440 grams of weight slinging around and the cranks are breaking close to the front.
Click to expand...


No edit I said grams here guys

And I said the lml BLOCKS need an lml crank so throws will clear webbing.

But this is a crank thread not a block thread or a balancer thread.

very sorry;)
 
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