To build or not to build?

[JoshH]

According to Jon’s research and findings, it’s not “work hardened” and adding the AF cam would not increase any risk to the crank, it only decreases it. If the crank already is fractured, there is no saving it though.

It’s not like a diff gear that does get work harden and create a pattern and changing that pattern can cause issues, noise or pre-mature wear. It’s like telling someone to NOT balance the rotating assembly on a used crank because it’s been ran that way for years. Balancing it only helps it

I personally don’t see a reason not to if it’s in the budget.

I know it's anecdotal evidence, but I put an alternate fire cam in SoCal built motor (replaced a 6460 standard fire for a 3388 alternate fire) a few years ago. The crank broke less than a month later. I've heard of others with similar results. Seems a like a little too much of a coincidence for me to recommend doing an alternate fire cam on a used crank anymore.

 

[Bateman1lml]

I know it's anecdotal evidence, but I put an alternate fire cam in SoCal built motor (replaced a 6460 standard fire for a 3388 alternate fire) a few years ago. The crank broke less than a month later. I've heard of others with similar results. Seems a like a little too much of a coincidence for me to recommend doing an alternate fire cam on a used crank anymore.

Thank you for this comment. You just saved me $1500! Lol


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[Chevy1925]

I know it's anecdotal evidence, but I put an alternate fire cam in SoCal built motor (replaced a 6460 standard fire for a 3388 alternate fire) a few years ago. The crank broke less than a month later. I've heard of others with similar results. Seems a like a little too much of a coincidence for me to recommend doing an alternate fire cam on a used crank anymore.

All other variables kept equal though?

Same has happened on guys that built thier engines and crank snaps a month later before af cams came out. Kyle had that happen on his.

IMHO, there is far too many variables to get a for sure answer. NRG is about the only way to be sure or do a l5p short block and mod for the crank sensor.

I may need to call my machinist and see if he’s seen any snapped cranks after doing the af cam. He’s not mentioned it to me since I turned him on to it for budget builds but I don’t know how many used cranks he’s putting blocks either

 

[JoshH]

All other variables kept equal though?

On the one we did, literally the only thing changed was the cam. The guy wanted a little bit more low end response, and we thought the smaller cam might help (it didn't really change it much in my opinion).

 

[JoshH]

Actually, I went back and looked through my records, it was a 9100 to a 6480AF cam swap.

 

[TheBac]

Changed the harmonics just enough to make a difference.

 

[Bdsankey]

I know it's anecdotal evidence, but I put an alternate fire cam in SoCal built motor (replaced a 6460 standard fire for a 3388 alternate fire) a few years ago. The crank broke less than a month later. I've heard of others with similar results. Seems a like a little too much of a coincidence for me to recommend doing an alternate fire cam on a used crank anymore.

Actually, I went back and looked through my records, it was a 9100 to a 6480AF cam swap.

Changed the harmonics just enough to make a difference.

This has always been my argument/thought but I have never had data to back it up from the Duramax platform other than a "that makes engineering sense" perspective.

 

[Bateman1lml]

So I picked up the new to me LML today. Since my blown up motor has ARP studs in it I want to swap them over to the “new” motor. Is it completely stupid to do them one by one to avoid taking the heads completely off and having them milled and what not. I think I know the answer to this question but I just need to hear it.


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[Bdsankey]

So I picked up the new to me LML today. Since my blown up motor has ARP studs in it I want to swap them over to the “new” motor. Is it completely stupid to do them one by one to avoid taking the heads completely off and having them milled and what not. I think I know the answer to this question but I just need to hear it.


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Which engine did you end up purchasing?

 

[2004LB7]

So I picked up the new to me LML today. Since my blown up motor has ARP studs in it I want to swap them over to the “new” motor. Is it completely stupid to do them one by one to avoid taking the heads completely off and having them milled and what not. I think I know the answer to this question but I just need to hear it.


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I've heard of people doing this successfully. I believe you only want to initially torque them enough to match the stock bolts. Then when you have them all swapped out you can start increasing the torque in stages like the instructions would say

 

[Bateman1lml]

Which engine did you end up purchasing?

The tow truck motor with 400k on it. Gunna slap a fluid damper on it. Possibly cp3 conversion and hope for the best


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[Bateman1lml]

The tow truck motor with 400k on it. Gunna slap a fluid damper on it. Possibly cp3 conversion and hope for the best


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Truck already had 370,000k on it so whats an extra 30,000


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[Bateman1lml]

Is there any threads on here about swapping head studs one by one?


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[JoshH]

I would strongly suggest pulling the heads and installing new head gaskets just so you can inspect the pistons. I can't tell you how many LMLs I've done head gaskets on and found small cracks around the edge of the bowl.

 

[Bateman1lml]

I would strongly suggest pulling the heads and installing new head gaskets just so you can inspect the pistons. I can't tell you how many LMLs I've done head gaskets on and found small cracks around the edge of the bowl.

Just looking at it here in the shop with a beer. Gunna do it fuck it. Full gasket kit deck the heads swap the head studs over. Fluid damper


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[Bdsankey]

Just looking at it here in the shop with a beer. Gunna do it fuck it. Full gasket kit deck the heads swap the head studs over. Fluid damper


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Solid plan!


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[DAVe3283]

I've done studs one at a time with good luck, but at the age of these engines now, and if the previous owner didn't change coolant every 5 years, the head gaskets are likely to be sus anyway. Your plan to do it right is the way to go, you'll not be wondering in the back of your head if the whole time this way.

 

[Bateman1lml]

I've done studs one at a time with good luck, but at the age of these engines now, and if the previous owner didn't change coolant every 5 years, the head gaskets are likely to be sus anyway. Your plan to do it right is the way to go, you'll not be wondering in the back of your head if the whole time this way.

Im 100% a back of the head guy. Thats why its all coming off. Just popped the metering valve out and there is 0 metal in it and that was supposed to be the issue with this motor. So there’s that lol



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[Bateman1lml]

She’s a head gasket motor it turns out


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[Chevy1925]

I would strongly suggest pulling the heads and installing new head gaskets just so you can inspect the pistons. I can't tell you how many LMLs I've done head gaskets on and found small cracks around the edge of the bowl.

100% this. Had the same crap happen.

If it was truck you drove in, pre 2011, and miles were lower, I’d slip stud it. Cummins guys do it all the time and I’ve seen guys on here do it. 2011+ hg suck though