Bore is 4.02. Standard honing diameter is 4.0165 +- .0008. These specs are from the 05 Dodge FSM. Top ring end gap, .010 - .014, second ring .033 - .045.
For high performance applications these are considered to tight. .007 - .009 is more generally excepted, but with coated pistons (sides AND tops), I go with .005 - .006. The coated tops helps keep the piston expansion down, and the coated skirts help reduce scuffing.
I use .023 for the top ring end gap. The second I leave at the factory end gap. The cummins top rings out of the box seem to be around .012.
These are spec and values based on a 05 CR.
Hope this helps.
Paul
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02 4x4 Auto Mach 6+'s, Drag Comp,Source Automotive Twins, Ultimate Transmission
05 2500 4x4 Auto 3.73 BBI 4's, Smarty Touch, Source Automotive Twins, F1 springs and Cam, Opie's bypass system, Mitusa, PPE Dual Fueler, Ultimate Transmission, Opie shafts,Isspro gauges
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