Stock Cummins Rod Breaking Point

2000wvdodge

2000wvdodge

Public Enemy
Joined
Dec 21, 2007
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So with all the different rod configurations out here today, whether they are stock, hardened (cyro, shot peened etc), or now the billet rod. What is the breaking point of a stock rod, when do you go from stock to hardened and hardened to billet? There are a lot of people that say you should just put a heavier rod in with a built motor but at what boost or hp limit can a stock one take?

Im not trying to open up a previous thread(s) that talk about the design or strength of the better stuff. I'm looking to hear how hot of a setup guys are running on stock rods and when they are changing over. And if it is a hot setup that failed due to stock rods how long did it live and what is the thoughts on them breaking. Some say lugging the motor drastically shortens the life, and some say if its turning a pile of rpms and the abrupt stop at the end kills them. This seems to be something that not many people either know the answer to or avoid the question all together.
 
I ran stock rods all last season without any rod failure but my truck is only a VP truck and was probably making around 700 horsepower.
 
I've kinda noticed a trend of the 5.9's goin billet once the 6.7's found out billet was needed to live at high levels. I can't figure out if efi opened tuning up so much they were needed for the 5.9's or it's just the awe of having billet's. Or possibly the tuning and the drag trucks spraying more. What happened to just the forged 12v rods being good for around a 1000 horse?
 
Figures. Can't find the smilie that's just throwing money away :lolly:
 
I remember hearing of pull truck hitting 1800 on shot peened/polished rods when I was looking at rods for my motor. I'd better go check my facts as it's been 2 years. This was also a low compression 5.9 however. I've got the same in my truck, and I'm very confident that they will hold up.
 
the price diff of nicely setup 12v rods and billet is about 1500-1800. so depending on how big of a build 1500$ isnt much!
 
StainlessRRA said:
I remember hearing of pull truck hitting 1800 on shot peened/polished rods when I was looking at rods for my motor. I'd better go check my facts as it's been 2 years. This was also a low compression 5.9 however. I've got the same in my truck, and I'm very confident that they will hold up.
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You are correct, BBD was running about that kind of power, but they were also only running 11:1 or 12:1 compression on a custom arias piston, on a half fill block. IIRC

With that being said you start playing with fire around 1000hp in a 12v and about 800hp in a CR, the dynamic timing of the CR adds a bunch of low end load that the 12v doesn't. CR rods and 12v rods seem to last until very similar power levels however when they do let go, CR rods tend to exit stage left (or right), and 12v rods shrink a bit first giving you some heads up.
 
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dvst8r said:
You are correct, BBD was running about that kind of power, but they were also only running 11:1 or 12:1 compression on a custom arias piston, on a half fill block. IIRC

With that being said you start playing with fire around 1000hp in a 12v and about 800hp in a CR, the dynamic timing of the CR adds a bunch of low end load that the 12v doesn't. CR rods and 12v rods seem to last until very similar power levels however when they do let go, CR rods tend to exit stage left (or right), and 12v rods shrink a bit first giving you some heads up.
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Exactly the truck I was referring to. That(and money since I get free machine work) was a big part of my decision. I doubt I'll ever push this truck past 1200, but we built it with that in mind.
 
it's been my experience that timing has a ton to do with it ... 34 degrees is my stopping point with stock rods.
 
Ok, so if 1000-1200 is the max on stock, when is a peened,polished, or cyro rod maxed out?
 
Wouldn't torque be the main factor? We know that torque is what is measured and the HP is mathematically derived. A CR making 1000hp at 3000 rpm makes a lot more torque then a 12v making 1000 at 4500. To make 1000 hp at 3000 you would need 1750 lb/ft of torque. If the stock rod can survive that then could it survive at 1750 lb/ft at 4500 rpm making 1500 hp or 5500 rpm making 1800 hp? Is this how BBD was able to do it lower torque at high rpm?

I really like this discussion and would like to see the torque aspect involved.
 
I think it depends too if it is a p-pump or a common rail. I think you can definately go much higher HP on a P-pump than a common rail on stock rods.. I think with careful tuning you can run around 1000 hp on a common rail, and I think that as John said timing will be your limiter on a ppump
 
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