Anyone found the limits of a 6.7 Cummins block?

morkable said:
Im hoping that because all I do is race I wont be in the rpm range that will cause a problem,, I do think though that I will get my TC loosened up some though,, the way I am looking at it is like this, if the engine is never in the danger zone for RPM it hopefully wont be a problem
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I missed this, what do you consider the danger zone?
 
zstroken said:
The filled blocks are even cracking cylinders. I don't think an external stiffener would do any better.
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The problem with filled block adding torsional rigidity is that the filler is so close to the center-line of the block and can't efficiently help torsion. It definitely can add reinforcement to the cylinders to withstand extra pressure, but if the theory is that the block is twisting and then cracking the cylinders then you need to move the point of reinforcement further away from the center-line to be the most effective. Same concept as I-beam rods vs. the X or + beam. I'm not saying it would work, just thinking out loud and throwing ideas out there.

Does anyone have a pic of the sides of a 6.7 block? I'm just curious how many threaded mounting points are there and where they are located.
 
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If you put ears on the deck plate and ears on the girdle, you could put standoffs in between with studs clamping the deck plate to the girdle. That's assuming there is room to do it.
 
RonA said:
If you put ears on the deck plate and ears on the girdle, you could put standoffs in between with studs clamping the deck plate to the girdle. That's assuming there is room to do it.
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I like the idea. Seems semi risky because any block torsion is translated directly into the mains. However, if it worked, you would have a near complete 'exoskeleton' that is tied into the front, back, top and mains of the block. If it didn't work, someone wasted a LOT of time! I sure it wouldn't be the first time that time got wasted on a random project. If someone was to attempt this and fail, more knowledge would be gained as to what doesn't work.
 
Smokem said:
Agco uses them, bore is 0.070" larger than a 5.9L, stroke is 0.480" longer. I bought a piston to measure out, I sold it.
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I wonder if this casting also has the steam holes???
 
I wonder if you could attach a flat plate spacer to the head between the head and intake manifold, then figure out a way to attach two or 3 standoffs to the girdle so that you could mount an adjustable proximity swithch on the end of each. Then by loading the engine on a dyno you could find out how much the girdle moved relative to the head. If your switch standoff was attached to the girdle near the rear of the block and ran up to a contat near the front it should show if it is flexing. Might even be able to make it work with a dial indicator and see how much with a direct reading under load.
 
RonA said:
I wonder if you could attach a flat plate spacer to the head between the head and intake manifold, then figure out a way to attach two or 3 standoffs to the girdle so that you could mount an adjustable proximity swithch on the end of each. Then by loading the engine on a dyno you could find out how much the girdle moved relative to the head. If your switch standoff was attached to the girdle near the rear of the block and ran up to a contat near the front it should show if it is flexing. Might even be able to make it work with a dial indicator and see how much with a direct reading under load.
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Great idea however would probably be more effictive to read it with an LVDT sensor instead of the prox switch.
 
on ours we actually drilled and tapped the steam holes to try and keep them from cracking. On six it was cracked in the back of the cyl so the steam hole wasnt the issue there on five it was more towards the exhaust side of the cyl im not gonna say tapping the holes helped anything hell it may have hurt it on cyl five but we got two good years out of the thing. It still ran decent jst was a ***** to start
 
Spareparts said:
on ours we actually drilled and tapped the steam holes to try and keep them from cracking. On six it was cracked in the back of the cyl so the steam hole wasnt the issue there on five it was more towards the exhaust side of the cyl im not gonna say tapping the holes helped anything hell it may have hurt it on cyl five but we got two good years out of the thing. It still ran decent jst was a ***** to start
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I was tempted to try that method with the steam holes, just hated to go thru all the work/money with a short block build and then have to hope it holds together.
 
GOT-Torque said:
I was tempted to try that method with the steam holes, just hated to go thru all the work/money with a short block build and then have to hope it holds together.
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No guts, no glory.LOL(no money):doh:
 
So does simply sleeving a 6.7 block down to a standard 5.9 bore help this cracking issue?
 
zstroken said:
They aren't even going that small, but why spend the extra coin on the 6.7 block?
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I got one for cheap. How small is needed for enough strength to handled 1200 HP? At what point does the extra stroke from the 6.7 crank become detrimental ?
 
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So I have a question,,, would I maybe be better off to scrap my 6.7 and find a 5.9 block and head and just use my existing 12v rods (that are in the process of being peened and cryoed) or keep going with the 6.7 and buy some billet rods etc.
 
Throwing in the 5.9 Crank and decking seems to be helping and no loss on spool up.

Friends is set up this way. Also so is Ashley Blacks I think.
 
SPEAKSUP said:
Throwing in the 5.9 Crank and decking seems to be helping and no loss on spool up.

Friends is set up this way. Also so is Ashley Blacks I think.
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Decking as in removing deck material? You're saying the extra stroke is the killer?
 
Im not saying anything LOL Ashleys is what atleast in the 1000 HP range and Matt's will be close to that once he gets the fuel.. But I think it was 5.9 Crank and taking .020 or something off the block to keep the compression right and etc. Just seems to be working...
 
Morkable a 6.7 crank in a 5.9 block makes a good combo since u already have good 12vlv rods all you would need is a new set of pistons. But theres really no need to do this until urs lets go if it ever does
 
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