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View Poll Results: Please pick the one that you had break
LB7/LLY 01-05 59 34.91%
LBZ/LMM 06-10 92 54.44%
LML 11+ 18 10.65%
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  #31  
Old 07-20-2010, 06:44 PM
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Originally Posted by GeorgiaDieselGTO View Post
Well I bought a truck with a broken crank, and after studying it all out, it is our inclination to think that it is caused by rpm more than anything. And i know that the guy that i bought it from would often take it up to 5000 rpms these motors are externally balanced which means that the weight of the balancer slinging around on the end of the crank is causing it to fatigue and eventually break. It is my thinking that an internally balanced crank in going to be the key to stop these failures.
Lets hear some more on this what is everyone elses thoughts? Oh and mine is an LBZ
So are you saying remove the balancer, and try just a balanaced crank?
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  #32  
Old 07-20-2010, 06:45 PM
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Originally Posted by whitetrash21 View Post
Ben?? as in Duratothemax.....???

What happened?
Just driving. Heard a "bang" and engine began missing and running rough. He looked underneath to see if any windows had appeared, and saw the balancer wobbling like everyone else has reported. He said he has to tear it down to make sure, but he's positive thats what it is.

He had towed 10,000lbs the day before. He thinks his engine's low oil pressure has a lot to do with this.

It sucks, but he was pretty upbeat in spite of it.
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  #33  
Old 07-20-2010, 07:40 PM
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dang that sucks. Someone mentioned that some of these cranks take more than others and it got me to thinking. It seems that way with these motors in general. Some will take a never ending pile of abuse with out missing a beat (bullfrog's bottom end comes to mind) while others just fall apart under normal driving. Its really weird.
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  #34  
Old 07-20-2010, 09:10 PM
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What about running "seasoned" cranks. I know it seems to work with intermidiate shafts behind Cummins. Has anyone noticed the miles on the cranks? Have you guys used high mileage cranks that was in the enigine before the build? What about new low mile cranks? Maybe you can brake down (no pun intended) the use before?

Did it come out of a engine that was babied or one that was beat on really hard?
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  #35  
Old 07-20-2010, 10:28 PM
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Originally Posted by 05' Ditry Duramax View Post
What about running "seasoned" cranks. I know it seems to work with intermidiate shafts behind Cummins. Has anyone noticed the miles on the cranks? Have you guys used high mileage cranks that was in the enigine before the build? What about new low mile cranks? Maybe you can brake down (no pun intended) the use before?

Did it come out of a engine that was babied or one that was beat on really hard?
Not a metallugrical expert by any means, but the whole "seasoned" thing seems a little wierd to me. Anybody have any data to back this up one way or another?

Seems to me a crank undergoes stress from twisting and bending. The basics say if you twist and/or bend something enough times, no matter how little, it will fail eventually in theory.

I suppose there is the work hardening thing that could apply as well, although I don't know how much (or even if) in this application.
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  #36  
Old 07-21-2010, 08:05 AM
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+1 for a broken LBZ crank. Whenever I get around to tearing it down ill post pics.

ben
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  #37  
Old 07-21-2010, 08:14 AM
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Originally Posted by duratothemax View Post
+1 for a broken LBZ crank. Whenever I get around to tearing it down ill post pics.

ben
Man, that sucks.... Sorry to hear that. Hope you get back up soon!
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  #38  
Old 07-21-2010, 08:39 AM
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Quote:
Originally Posted by duratothemax View Post
+1 for a broken LBZ crank. Whenever I get around to tearing it down ill post pics.

ben


Well Ben,


Your mother told you to STOP your wrecking a good truck!


Good luck,lil buddy
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  #39  
Old 07-21-2010, 09:10 AM
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Originally Posted by MACKIN View Post
Well Ben,


Your mother told you to STOP your wrecking a good truck!


Good luck,lil buddy
I just have to laugh, ironic that out of the 3 motors that have been in my truck, the one I ran the hardest with the littlest care to anything was my stock factory original engine...and everyone says LLY's are junk... : That made it 85-someodd thousand miles before cracking a piston. My "BUILT" motor lasted 15,000. This stock LBZ POS short block lasted about 50,000. Wonder how far Ill get on lucky #4.

ben
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Last edited by duratothemax; 07-21-2010 at 09:10 AM.
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  #40  
Old 07-21-2010, 10:36 AM
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Quote:
Originally Posted by duratothemax View Post
I just have to laugh, ironic that out of the 3 motors that have been in my truck, the one I ran the hardest with the littlest care to anything was my stock factory original engine...and everyone says LLY's are junk... : That made it 85-someodd thousand miles before cracking a piston. My "BUILT" motor lasted 15,000. This stock LBZ POS short block lasted about 50,000. Wonder how far Ill get on lucky #4.

ben

my factory lly engine is still good (135,000 miles), hope I dodge all these bullets, sorry to hear about your bad luck Ben, hopefully # 4 is the last
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  #41  
Old 07-21-2010, 10:47 AM
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I know WDINO73 lost a crank in his built LB7 as well. As for the seasoned block theory, there may be some truth to this. I know the 6.5's have a history of cracking in the main webs on the new style squirter blocks, but blocks that seem to last to 100K miles or so without cracking seem to hold up to most anything after that. They also have problems with heads cracking between the valve seats, but seasoned heads without cracks seem to last as well.
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  #42  
Old 07-21-2010, 10:53 AM
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Originally Posted by LarryJewell View Post
my factory lly engine is still good (135,000 miles), hope I dodge all these bullets, sorry to hear about your bad luck Ben, hopefully # 4 is the last
Larry you need to run some man tuning... those twins should make 800+ on stock injectors.
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  #43  
Old 07-21-2010, 11:26 AM
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Quote:
Originally Posted by duratothemax View Post
I just have to laugh, ironic that out of the 3 motors that have been in my truck, the one I ran the hardest with the littlest care to anything was my stock factory original engine...and everyone says LLY's are junk... : That made it 85-someodd thousand miles before cracking a piston. My "BUILT" motor lasted 15,000. This stock LBZ POS short block lasted about 50,000. Wonder how far Ill get on lucky #4.

ben
Sorry to hear but how many miles were on the LBZ before you installed it?
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  #44  
Old 07-21-2010, 12:22 PM
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Originally Posted by ripmf666 View Post
Sorry to hear but how many miles were on the LBZ before you installed it?
no idea...it was a GM test engine. So I guess 0 "miles" in an actual truck, but who knows what GM did to it when they were testing it on the dyno.
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  #45  
Old 07-21-2010, 01:19 PM
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no idea...it was a GM test engine. So I guess 0 "miles" in an actual truck, but who knows what GM did to it when they were testing it on the dyno.
Sorry to hear that Ben.

If you need a hand, let me know.
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