Anyone found the limits of a 6.7 Cummins block?

I personaly dont think its anything with the rpm on these blocks its in the cylinder design they have got to be flexing or twisting some the block that we cracked was on cyl five and six and was fully filled
 
Are they splitting on a casting line? What are sonic tests showing?
 
Well phuck, this thread isn't giving me the warm fuzzy about the 6.7 at all.......Anyone have any photo's of the deck plate and associated machining?
 
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Has anyone looked into the 6.7 industrial/marine blocks to see if they are any different?
 
Mopar Muscle said:
Has anyone looked into the 6.7 industrial/marine blocks to see if they are any different?
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Don't believe they are, as I was thinking the rear gear 6.7CR are even the same casting.

There is a high HP military app that is made from a different materal, but those blocks are nearly impossible to come by last I had checked.
 
Mopar Muscle said:
Has anyone looked into the 6.7 industrial/marine blocks to see if they are any different?
Click to expand...

I'm pretty sure the I saw on Quickserve a 6.7 engine that had the same bore as a 5.9 but a much longer stroke to make up the needed displacement. I'm thinking it was engines destined for medium duty trucks or ag application.
 
lorendiesel5.9 said:
I'm pretty sure the I saw on Quickserve a 6.7 engine that had the same bore as a 5.9 but a much longer stroke to make up the needed displacement. I'm thinking it was engines destined for medium duty trucks or ag application.
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Pretty sure that is an ag application from over seas. It is a rear gear train block if I remember correctly and finding one is pretty much impossible.
 
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.
 
I'm not worried about it on this one. I want to see the difference first hand between the 5.9 and the 6.7, and if it breaks and doesn't screw up the rods or the head, it won't cost that much to try again.
 
I agree Ron. I'm kinda stuck anyways, can't afford to change gears now
 
morkable said:
I agree Ron. I'm kinda stuck anyways, can't afford to change gears now
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I talked to Zach about a less aggressive cam(bottom end wise) so I may change that and the jet going to the afc to slow down the fuel.
 
So, if several people think the cylinders are cracking due to block flexing and not cylinder pressure, what would be the thoughts on making an external block stiffener braces? It could bolt between the engine and the transmission like a mid-engine plate and also in the front like a front engine plate. Between the would be external structural braces in an 'X' shape on either side to help with overall block rigidity.

Any merit here, or just a hair-brained idea?
 
Mopar Muscle said:
So, if several people think the cylinders are cracking due to block flexing and not cylinder pressure, what would be the thoughts on making an external block stiffener braces? It could bolt between the engine and the transmission like a mid-engine plate and also in the front like a front engine plate. Between the would be external structural braces in an 'X' shape on either side to help with overall block rigidity.

Any merit here, or just a hair-brained idea?
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The filled blocks are even cracking cylinders. I don't think an external stiffener would do any better.
 
RonA said:
I talked to Zach about a less aggressive cam(bottom end wise) so I may change that and the jet going to the afc to slow down the fuel.
Click to expand...

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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