Broken Crankshaft Count?
- Thread starter EDP
- Start date
Only if the guys that offer the cams know the firing order............ been down that road, no thanks
To clarify I was proposing the new order to be 12734568 were 3 and 8 would be swapped
12734568 is the same order as the 7.3 6.0 and 6.4 powerstroke and they dont seem to have any problems
12734568 is the same order as the 7.3 6.0 and 6.4 powerstroke and they dont seem to have any problems
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It's how the crank is rotary-forged. It works most the time. But in others, it puts a micro-fracture in from the factory. Some break at at OEM horsepower, others survive past 1000HP.
I'm lucky. I have both LLY and LBZ engines, from 500 to 1000 hp. Never broke a crank.
I'm lucky. I have both LLY and LBZ engines, from 500 to 1000 hp. Never broke a crank.
Yes, the 12734568 firing order is possible. I meant the 15426378 firing order can't be done without a different crank.
Yes 15426378 is fords gas v8 firing but there cylinders are numbered different so for a duramax to fire in the same order it would be 12734568. I can see were the confusion can come from in my post
Yes correct
We have ran Ford firing orders as well as what we are currently running and no crank modifications.
We did run into a situation where two cams went out with the Key cut 180 off and those issues have been resolved.
What were the results of runing the modified firing order? smoother runner? more power, less power?
We have not broke one crankshaft with the alter fire pattern. Obviously I cant say who is all running them but they are in some of the top 3.0 trucks in the country and a few 2.6 as well. Knock on wood. Smoother harmonics, from relieved cylinder pressure. Power gains are minimal when comparing cam grind to cam grind.
How would firing order have anything to do with cylinder pressure? I get the fact that spreading out the pulses across the crank surface will distribute the stress better, but what happens inside the cylinder will not be changed given the tuning stays the same and the cam profile stays the same.
Add me
Add me to the list of broken lmm crankshafts. 2007.5 3500 new style dully 118k on an all stock truck, has lived a life of daily driving and weekend towing of horses. Truck was running fine got a low oil pressure light warning, checked oil was fine engine started to knock and it was all down hill from there. Pulled oil pan and found crank snapped in the 5/6 area and also broke through the counter weight on the shaft, ill try to post some pics tomorrow. We got a used engine with 47k on it for a transplant. Hope this helps
Add me to the list of broken lmm crankshafts. 2007.5 3500 new style dully 118k on an all stock truck, has lived a life of daily driving and weekend towing of horses. Truck was running fine got a low oil pressure light warning, checked oil was fine engine started to knock and it was all down hill from there. Pulled oil pan and found crank snapped in the 5/6 area and also broke through the counter weight on the shaft, ill try to post some pics tomorrow. We got a used engine with 47k on it for a transplant. Hope this helps
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What year model is your LMM? I know waranty isnt what it use to be but back in the day if the term wasnt up they would work with you on the miles. In other words 3 year 36k mile waranty the dealer could arthorise a repair on a truck with 40k on it if the 3 years wasnt up.
Edited post sorry about that. This does concern me as we bought this truck to tow some weight (in the 6k to 10k range) and these donor engines Are NOT CHEAP! I will say after the hastle of pulling the front of the truck off I think I would just as soon remove the entire cab from the chassis next time to do the motor. We have a 3 bay garage with lifts available and removing the body mount bolts is a piece of cake for us, and simply lifting the cab off the chassis.
So out of curiosity how many lmm members does that make whom have broken stock trucks? And has ANYBODY gotten an affirmitive answer from GM or otherwise as to why this keeps happening? 
118k on a diesel should be nothing! Especially if it is well maintained and not beat to death. I could understand if the motor was lugged this happening but this is an automatic, has never been lugged.
118k on a diesel should be nothing! Especially if it is well maintained and not beat to death. I could understand if the motor was lugged this happening but this is an automatic, has never been lugged.i bought the truck that way. It looks like it was taken care of. It has a set of mpi towing twins on it with 30 over injectors. It has 140k on it. I took some pictures of the crank that I will post up here. I have a theory of why they are breaking but it would be hard to prove.
