2015 6.7l ARP 425 vs 625

**E.mccarthy7018** · 03-06-2016

Ok, it seems like all the talk is for the 625 studs and noone even talks about the 425. I guess my question would be does anyone know what the stock head bolts are rated for to compare to the 425's?

i know the 625's treated to 260k psi, tirqued to 150 ft/lbs
the 425's are treated to 200k, torqued to 125 ft/lbs
how much stronger are they than stock bolt and what would be possible scenerio for needing either one?

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**TH-64** · 03-07-2016

Subscribed: I would like to know this as well.

Thomas: 2012 Saddle Brown CCSB

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**68muleteem** · 03-07-2016

I found a source that quotes 176k for stock bolts, not sure but that could very well be true. Not a big difference, but the studs are not being turned over the length, only pulling force on them. They will stretch over time but are not "twisted" into place like a bolt.

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**E.mccarthy7018** · 03-07-2016

176k sounds right. I see a bunch of guys using the allen head bolt that are rated for 190 which is right under the 425's yet over 300$ cheaper. Just havent seen them using them on these newer 6.7s( not sure how
much of a difference it makes)

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**E.mccarthy7018** · 03-08-2016

I am still curious to know when it would be necesary to go to some upgraded bolts or studs. I dont really want to go all out with 625's because I dont plan on any more performance mods other than maybe some slightly better injectors (50s) if i ever start having issues with the stock ones. Other than that just raceme ultra for now.

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**DRD** · 03-08-2016

Studs are a good investment for more than tensile strength. Look at the mechanics of a stud and how it applies clamping force.

Bolts will have torsional stress on them from the bolt head down to the last thread when torque down. To some degree, this limits clamping force.

Studs are installed without bottoming out the threads in the block. The only torsional stress is at the tip where the nut is. This provides pure linear clamping force on the head.

Ray
Double R Diesel, LLC
www.doublerdiesel.com
info@doublerdiesel.com

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**E.mccarthy7018** · 03-08-2016

Ray you give a thorough explanation everytime!

With my application listed before do you believe a 425 or (2000) would suffice for what im doing?

i see you carry both the 425 and 625 on your website and assume if you didnt believe in the 425 you just wouldnt carry them, yet all the "opinions" ive read on other sites ( and ive read ALOT) all seemed to be along the lines of "just put the 625s in because they are better". do you think the 425s are underrated?

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**DRD** · 03-08-2016

Originally Posted by E.mccarthy7018

Ray you give a thorough explanation everytime!

With my application listed before do you believe a 425 or (2000) would suffice for what im doing?

i see you carry both the 425 and 625 on your website and assume if you didnt believe in the 425 you just wouldnt carry them, yet all the "opinions" ive read on other sites ( and ive read ALOT) all seemed to be along the lines of "just put the 625s in because they are better". do you think the 425s are underrated?

Here's the deal...

425s are great and do the job. They will stretch just ever so slightly over a period of time, thus its recommended to retorque them after a few heat cycles.

625s are indeed pricey, but torque them once and you're done. They don't stretch. I put them into my own 2012. I'm not planning on opening my valve cover again until injector replacement.

You can find my 625 install in the "how to's" on this forum.

Ray
Double R Diesel, LLC
www.doublerdiesel.com
info@doublerdiesel.com

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**beans20** · 03-08-2016

Originally Posted by E.mccarthy7018

Ray you give a thorough explanation everytime!

With my application listed before do you believe a 425 or (2000) would suffice for what im doing?

i see you carry both the 425 and 625 on your website and assume if you didnt believe in the 425 you just wouldnt carry them, yet all the "opinions" ive read on other sites ( and ive read ALOT) all seemed to be along the lines of "just put the 625s in because they are better". do you think the 425s are underrated?

I think it's more of a security measure. With an investment of 60k in a pickup why not just do it once and be done with it. That's always been my motto. You might not being planning on doing anything crazy at this point as far as mods go, but what happens later on down the road after that warranty wears out a little more? In the event that you did buy the 425's and they did not hold up to what you have done, you will spend twice the amount of money repairing the damage done as well as buying the 625's at the end of the day. I'm not trying to sway your decision one way or the other but that's my philosophy. I don't want to spend more in the long run because I am a cheapo, I'll just save that little bit of extra money up front and have that security for that extra $500 versus $5k or more. I am currently in the process of saving money for head studs now, I was also in the same boat debating 425's over 625's. But I'll save that money up front and get it over with. @Double R Diesel, you better be ready for that email when it's time!

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**DRD** · 03-08-2016

Just FYI fellas. I'll sell premium members of igotacummins.com either 425s or 625s for a price near my cost. I consider studs such a wise investment that I'll do that for premium members.

Ray
Double R Diesel, LLC
www.doublerdiesel.com
info@doublerdiesel.com

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