After I had my LBZ break the crank, I looked it over very carefully. Mine broke behind 1&2 rod journal. What I have gathered is there is not enough bearing surface on number 1 main for all the pressure and weight on the snout of the crank. I think harmonics play a role in it. I was looking at the serpentine belt and how much force that actually pulls up on the crank. I think that is a big contributing factor to the cranks that break where mine did. I would like to see what it would do if you could put another serpentine belt on the damper pulley pulling with the same force in the opposing direction to see what that would do. Just a thought I had.
Cranks
- Thread starter Fingers
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Are we ruling out cap-walk and still considering misalignment then? It may very well be alright until the block settles after so many miles and begin to moveout of alignment as miles grow, this also brings to mind how thick is the bottom end on these engines?
Fingers, anyone, would you happen to have a thought to maybe a 'compounding' harmonic load per say causing these to breaks in addition to a load of pull X amount of mentioned by gmac32 as well as Mr. brady.
Fingers, anyone, would you happen to have a thought to maybe a 'compounding' harmonic load per say causing these to breaks in addition to a load of pull X amount of mentioned by gmac32 as well as Mr. brady.
Duramax firing order is 12784563 90% of crank failure we have scene is in the 1-2 rod or main journal area. add the 1&2 next to one another in such quick fashion, and all the weight out front magnifying the already known issue.
Sound waves and harmonics in a motor also I think are tied to the issue. We have done a few different patterns to try and spread out the bang effect and knock on wood to date have yet to see any of the cranks fail after the swap was done. This is going on 3 years and many of the top running sled pulling trucks in the country, along with many street trucks. I can not mention names but those that are out there running this setup feel free to jump in and give your .02.
I don't know half of what all of you are talking about. but as far as the load on the crank from the serpentine. I was going to ask if a lot of the early trucks like mine that's an 01 break cranks. it has a different tensioner setup. I actually thought is was bad when I bought it because the tensioner tends to just bounce a lot, at idle anyway. replaced it and it still does it. just something to think about. and I read in diesel power about super charging your diesel duramaxes had a lot of problems with cranks breaking. but I guess that could be from the explosive throttle response they describe. as far as equaling load on the crank front to back I would think the drag from the super charger would help not hurt. like I said just throwing stuff out there you probably already know. but didn't figure it would hurt.
Material is 5140, better material helps
External balance is standard, Internal balance helps
Standard fire order does put stress on the front and middle of crank, Altering the fire order may help
These parts are heavy and intended for under 3000RPM , now add power and RPM... Pressure on crank become exponetially greater, Minimizing the inertial weight will help.
Any of the above can and will trigger a harmfull harmonic, or different one's.
OH BTW the Model in the first post seems to be incorrectly projected, because the main jurnal cant move vertical nearly as far as the model shows when in a engine with out counterweights hitting things. Also the peak forces seen in a crankshaft are torsonal, and lateral on the rod jurnal. Not really pulling apart like an accordian as it seems to be doing. Static forces and dynamic forces will be completely different. IMO But i could be looking at it wrong too.
External balance is standard, Internal balance helps
Standard fire order does put stress on the front and middle of crank, Altering the fire order may help
These parts are heavy and intended for under 3000RPM , now add power and RPM... Pressure on crank become exponetially greater, Minimizing the inertial weight will help.
Any of the above can and will trigger a harmfull harmonic, or different one's.
OH BTW the Model in the first post seems to be incorrectly projected, because the main jurnal cant move vertical nearly as far as the model shows when in a engine with out counterweights hitting things. Also the peak forces seen in a crankshaft are torsonal, and lateral on the rod jurnal. Not really pulling apart like an accordian as it seems to be doing. Static forces and dynamic forces will be completely different. IMO But i could be looking at it wrong too.
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I'm not a metal guy by any means, but I have broken a few cranks in the years, all in my race truck. I broke one and it snapped the front off the crank leaving the journals alone. I knew it was broken but was competing in an event. The truck still ran 9's at over 140mph but was missing badly because of the crank sensor getting wacked by the reluctor wheel. Bearings looked great and that engine had been beaten on badly all season.
Just a different experience that may contribute to the discussion.
Just a different experience that may contribute to the discussion.
Rob on the engines that broke the cranks, how did your bearings look? Some are thinking its a main cap alignment issue. Just curious as to what you have seen. I only have the one crank and it has no wear marks or heat damage to the fillet, which tells me alignment was good.
I don't believe it's cap alignment per say, but block twist may be a factor. Two of the blocks that cracked cranks also had bad cracks in the main journals. These were before SoCal did my engine. I have seen totaled bearings without broken cranks and broken a crank with bearings that look perfect.
Summary to this point
What I have heard here and seems to follow:
Things that seem to increase the chance of a broken crank:
Things that seem to decrease the chance of a broken crank:
What I have heard here and seems to follow:
- Cranks breaking at all power levels.
- Breaks mainly on the #1 throw. Along the throw fillet propagating from inside out.
- Bearing wear and main walking do not appear to be root causes.
- Main alignment does not appear to be the issue.
Things that seem to increase the chance of a broken crank:
- heavy loads on the accessory pulley. (Blower)
- Some Harmonic Balancers
Things that seem to decrease the chance of a broken crank:
- Alternate firing order. (which order?)
I would add Dual CP3 as an accessory load on the crank pulley as well.
I wish someone would come up with an accessory drive off the gear train with a front cover that didn't cost your first born to run. It would move the load on the crank a little closer to the #1 main.
Or like mentioned a larger bearing or seal/bearing combo in a stronger front cover (billet). That would definetly not be cheap though.
I wish someone would come up with an accessory drive off the gear train with a front cover that didn't cost your first born to run. It would move the load on the crank a little closer to the #1 main.
Or like mentioned a larger bearing or seal/bearing combo in a stronger front cover (billet). That would definetly not be cheap though.
Any load on the accessory side is going to effectively increase the inertia of that end of the crank.
What is the alternate firing order of the Empire Cam? I've been doing some basic torque analysis on the crank and am amazed how much force a throw puts on the adjacent throw on the crank. Especially when the throws are 90° from each other.
What is the alternate firing order of the Empire Cam? I've been doing some basic torque analysis on the crank and am amazed how much force a throw puts on the adjacent throw on the crank. Especially when the throws are 90° from each other.
Did a little research on firing orders.
Caterpillar
3208-3308-3508: 1,2,7,3,4,5,6,8
3408: 1,8,4,3,6,5,7,2 (same as duramax)
Duramax
1,2,7,8,4,5,6,3
Power Stroke
6.0: 1,2,7,3,4,5,6,8
6.4: 1,2,7,8,4,5,6,3
Maybe the 6.0/Cat would be a better option?
Jon, anyway to plug these into a crank load simulator?
Caterpillar
3208-3308-3508: 1,2,7,3,4,5,6,8
3408: 1,8,4,3,6,5,7,2 (same as duramax)
Duramax
1,2,7,8,4,5,6,3
Power Stroke
6.0: 1,2,7,3,4,5,6,8
6.4: 1,2,7,8,4,5,6,3
Maybe the 6.0/Cat would be a better option?
Jon, anyway to plug these into a crank load simulator?
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You have to keep in mind the twist on the crank. That is, does the first throw lead or lag the second throw. Ford and Chevy being opposites.
Still looking for the order used on the EDP cam.
Still looking for the order used on the EDP cam.
Know of a few cranks that let go towing with the cruise control on. Not sure if it was from extended times at that setting that made it let go or if it was just hanging on and happened to let go at that time.
That's what happened with mine. Several hours cruising at the same rpm with minor changes on hills. Then a vibration that slowly got worse till after 5 min of it I pulled to the shoulder and it shut it down and it never ran again.
However as I said before, I think my problem was compounded by the loose converter bolts over time, maybe the steady rpm did it in, who knows.
The End Cam order we are running is different then those all listed above.
We did use a couple variations before we got to where we are at now.
Customers running Alter Fire Cam
Sled Pulling Application:
Open Unlimited: 1
3.0 Pro Stock Class: 6
2.6 Street Diesel: 14
Street Trucks 18
Drag Race Only Application: 2
We did use a couple variations before we got to where we are at now.
Customers running Alter Fire Cam
Sled Pulling Application:
Open Unlimited: 1
3.0 Pro Stock Class: 6
2.6 Street Diesel: 14
Street Trucks 18
Drag Race Only Application: 2
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