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Discussion Starter · #1 ·
I have a crazy idea to install a 6.7 crank into my 1st gen non IC...I know, I know, it's a really small stroke increase and probably not worth the trouble. But what if I just want to do it anyway? I do believe that to make a 6.7 crank work in a 5.9, the pistons will need to be shaved .080"
Is there enough "meat" to trim? And yeah, I know bowl volume will decrease a bit, but I'm ok with a mild compression bump
Thx
Ed
 

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The 5.9 engine is 4.02" bore x 4.72" stroke and the 6.7 is 4.21" x 4.88". That's .160" longer stroke, not .080". That would be a lot to shave off the top of the piston plus you'd be raising the compression ratio a considerable amount. Cummins had a 4bt 4.5 that had a 4.02" bore and 5.43" stroke. Those pistons wouldn't work because they would come up short. About the only solution would be pistons with a custom pin placement which would be kind of pricey. A lot of expense for very little pay back.
 

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Discussion Starter · #3 ·
Yes, the 6.7 crank has a .160" longer stroke, but you need to divide that difference in stroke by 2 since the "additional" stroke is split between TDC and BDC. Half of .160" is .080"

So can pistons be shaved tha much or is there an alternative, such as trimming a little less and using a thicker head gasket?

Ed
 

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Yes, .080" can be taken off no problem.
 
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Yes, it has been done. The non-IC first gen pistons have no problem losing .080" from the tops.

Why not do a mechanical 6.7 though?
 

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Discussion Starter · #7 ·
Not really interested in a 6.7 at this time, thanks

Ed
 

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I wouldn't modify a cast piston in any matter. Just do a head gasket and rest assured that you aren't going to blow a piston to pieces... at least immediately.
 
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