Anyone found the limits of a 6.7 Cummins block?

Mopar Muscle

Mopar Muscle

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Has anyone found the limits of the 6.7 Cummins block? I'm not talking about stock short blocks, but physical limitations of the main area due to power or cylinder walls cracking do to pressure?
 
I would say 1300-1400HP and your living dangerously.
 
Pretty sure Haisley's last one is based off a 6.7, with liners that likely put them back in the 5.9 displacement range, but gaining good wall thickness along with the strength of the siamese bores. Pretty sure 6.7 crank too. 1800+?

I've had a 6.7 here for three years still not sure just how I'll go with it.
 
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Ron what happened to the build?
Also I think if the block was filled and sleeved it would be fine. There was a thread on here last year that talked about darton sleeves,being the ones to go with. Not sure of its limit though
 
We have had zero problems with any of the blocks. Not making anywhere close to the power of some of the sled pullers are though. Im guessing we are around the 1000hp mark and 140psi boost. Just using stock main bolts also.
 
Joesixpack said:
Pretty sure Haisley's last one is based off a 6.7, with liners that likely put them back in the 5.9 displacement range, but gaining good wall thickness along with the strength of the siamese bores. Pretty sure 6.7 crank too. 1800+?

I've had a 6.7 here for three years still not sure just how I'll go with it.
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They also use a deckplate as well. The 6.7 deck is weaker than a 5.9 with all the additional steam holes.

So if you want to make big power and not have to worry about your block surviving, you better run a deck plate and sleeve each cylinder.
 
That's basicly what i was told. 5.9 will handle more power at less than 1/2 the parts/machining price. Mine will just end up a modest powered daily driver with no fancy parts. That's the down side of trying something new.
 
Blacksdieselhp said:
We have had zero problems with any of the blocks. Not making anywhere close to the power of some of the sled pullers are though. Im guessing we are around the 1000hp mark and 140psi boost. Just using stock main bolts also.
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I'm sure rods are not stock. What is your preference at this level? Suped up 12v rods or billet rods?
 
how much money does it cost for the sleeves,deck plate and all the machine work and is it worth it.
 
dmaxexpress said:
how much money does it cost for the sleeves,deck plate and all the machine work and is it worth it.
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Define worth it. LOL If you want the block to make it more than 10 passes I would say it is worth it, if you don't mind sticking a new block in ever 5 or so passes then probably not.
 
If it let's you hang with the billet blocks it would be a bargain. Now I thought some org's were not going to allow deck plates, which makes no sense....
 
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Joesixpack said:
If it let's you hang with the billet blocks it would be a bargain. Now I thought some org's were not going to allow deck plates, which makes no sense....
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If an org doesn't allow deckplates they won't allow billet blocks. There were some orgs that were pushing for aftermarket blocks also.
 
zstroken said:
If an org doesn't allow deckplates they won't allow billet blocks. There were some orgs that were pushing for aftermarket blocks also.
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define "billet" ?

What if it is an "oem appearing" block? :poke:

Here we go again... :doh:

It's all about semantics and gray areas. LOL
 
GOT-Torque said:
define "billet" ?

What if it is an "oem appearing" block? :poke:

Here we go again... :doh:

It's all about semantics and gray areas. LOL
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Aftermarket blocks were specifically prohibited. Billet would fall into that category. There were targeting not allowing cast aftermarket blocks.
 
Haisley is at around 2,000hp, but it took a lot of machine work to get there.
 
The 6.7's that have survived 1,000+ hp have all been with large singles with less useable torque down low. I'm planning a triple build with my 6.7, so I'm worried about the block handling 1,800-2000 ft-lbs at low to mid rpm levels. It seems that compounds on 6.7s seem to be the killer (usually rods). Just wanting to find out what I need to worry about if I have a set of billet rods, pistons that will hold up, and a real girdle. A reputable source on here told me that the cylinders can crack. I just wanted to see if I could find a first-hand witness to this problem.
 
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