Broken Crankshaft Alt Fire Cam

[Ne-max]

This is where I got my new crank from. Cheapest price I found with reasonable shipping. I myself had a couple used available but did not want to risk it.

http://www.genuinegm.com/parts/2002/Chevrolet/Silverado%202500%20HD/Base/index.cfm?action=partDetail&section=ENGINE&group=CRANKSHAFT%20%26%20BEARINGS&subgroup=CRANKSHAFT%20%26%20BEARINGS&component=CRANKSHAFT&partnumber=97225901&vehicleid=96611&siteid=215088

 

[S Phinney]

It was a used crank that I got from Dustin aka Othrgrl. It tested out just fine. It did have a standard order cam ran on it and I switched to the alt fire cam. It was capable of well over 1000hp. There isn't a real answer for breaking cranks. There are several ways to minimize it I suppose. Jeremy at Wagler is using Winberg cranks. They are the only ones that don't have any posted failures. They cost about 4500 bucks retail. I am going with the LML crank with internal balancing this time. The LML is very similar to the lb7 but it is harder than the other cranks. I posted to let people know that it happens even though I already knew myself that it had.

 

[Potthoffdmax]

I appreciate the honesty!!!

 

[DIESELMAFIAPER.LB7]

I'm wondering it was becuase it was stressed already? Have people been breaking new cranks with af cams?

 

[LBZ]

Used crank. Nuff said.

Don't care how well you can "externally" check a crank for cracks, it can be cycled and stressed to the point just before it shows cracks and you won't see it.

Until I see multiple engines with AF cams that started with new cranks breaking I'm going to believe the AF helps the issue.

 

[zf>allison]

It's a gm curse. Like the 6.2 and 6.5 lol

 

[duramaxdiesel]

That seriously blows! I'd be pissed too. Talk about discouraging. Let us know how it goes with a new LML crank.


Nick

 

[motoking_1990]

It's a gm curse. Like the 6.2 and 6.5 lol

These were very good engines.........for yard ornaments

 

[S Phinney]

Used crank. Nuff said.

Don't care how well you can "externally" check a crank for cracks, it can be cycled and stressed to the point just before it shows cracks and you won't see it.

Until I see multiple engines with AF cams that started with new cranks breaking I'm going to believe the AF helps the issue.

I can assure you that it was no it cracked.

 

[WolfLMM]

I know everybody says it hasn't happened. They say that the alternate firing order camshaft is the cure. I am here to tell you guys that isn't so. I have proof that they can still break. View attachment 38248

If this is a used crank (used with std firing order cam), then it doesn't mean anything. The damage had already started.

Edit: Just to hammer this point home, the material can have micro cracks internally. Your engine machine shop cannot detect this.

 

[zf>allison]

These were very good engines.........for yard ornaments

There good for first diesels for kids like I was. And fuel mileage. Other than that ur right. Just weird those had a crank failure problem as well

 

[LBZ]

I can assure you that it was no it cracked.

Not saying it was cracked (and I'm sure visually it looked tip top) but curious as to what method(s) was used to inspect it.

Again a used crank has been previously cycled and stressed. And possibly (likely even) different than from how it would with an AF cam. There is no way to measure this and there is no constant because every engine is different depending on how it is tuned and run.

Using a used crank throws an unknown variable into the equation when trying to determine if the AF cam solves or reduces the amount of crank failures. There is no way to know for sure in this case if it helps or not.

 

[moparkxracer]

Has anyone broke a new crank with an AF cam?

 

[Turbo Performance]

Sorry to see this Shane. So even after seeing this, why is everyone still hellbent that AF cam is the answer and this HAD to have been caused previously by the standard fire cam?

 

[WolfLMM]

I don't think everyone is hellbent that AF cams are the Complete answer, but they obviously help.

 

[OregonDMAX]

I can assure you that it was no it cracked.

May not have been cracked but it could have been stressed. Also, only an NDT test could see micro cracks deep in the crank that magnafluxing will not show.

 

[LBZ]

I don't think everyone is hellbent that AF cams are the Complete answer, but they obviously help.

^^^This

May not have been cracked but it could have been stressed. Also, only an NDT test could see micro cracks deep in the crank that magnafluxing will not show.

And this. And for the cost of NDT, you can almost buy a new LML.

 

[prostreeter600]

Sometimes trial and error is the only way when all the mathematical equations and engineering fails to explain and or solve the problem. Until we get the R & D done with a new crankshaft paired with an AF cam there will be doubts and concerns . I personally would like to know what the magic combo is that isn't gonna cost me another 5-10k once I get back together and then have it break another crank . I say another cause I've broken 1 LBZ already . I guess only time will tell

 

[S Phinney]

If the crank could be redesigned it would be better. Space inside the crank case is the limiting factor. That is why Winberg probably is the best crank out there right now. You have to justify the cost to buy one. I don't have the funds to spend it on one right now. There isn't a real answer either so I have to use my best available options.

 

[OregonDMAX]

^^^This

And this. And for the cost of NDT, you can almost buy a new LML.

Well I mentioned that because what I do for a living is rebuild ski lift chair grips and we have to NDT them so I got my own machine . Didn't realize the cost to have something NDT'd was so expensive

But it will show some micro cracks you wouldn't ever expect to be there