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KB hypereutectic pistons are excellent IF you follow their guidelines.

The machinist needs to pay close attention when finish honing. KB hypereutectic pistons require a tighter fit in the cylinder (because of their alloy properties and rigid skirt design). This will also affect your piston ring end gaps, so make sure your machinist is aware of the special KB suggested piston to wall clearance.

The top ring end gap also requires special attention, because of their unique thermal conductivity and ring land location. Gap the second ring to factory specifications. KB pistons also feature an accumulator groove, which is a groove between the two compression rings. Cylinder pressure that get trapped between the first and second compression rings tend to unseat to top ring. This causes ring flutter and ineffective piston ring seal. The void created by this groove between the rings, tends to relieve the spike pressure of combustion, keeping the pressure low enough to prevent lifting the top ring while maintaing some preload on the second ring. Read this to learn more on what makes these pistons so durable:

KB hypereutectic pistons will withstand alot of punishment and have respectable longevity, IF you follow the special piston to cylinder wall clearances AND piston ring end gap. Too many engine builders fail to comply with these requirements, then blame the pistons to be at fault. Please read the chart at bottom of this link to find your tolerances (piston bore clearance & top ring end gap):

The wrist pin bore does intersect the oil ring groove on stroker pistons (4.140" and higher stroke). There are currently three methods (that I know of) being used to rectify the oil consumption issue.
1. wrist pin bore "pin button"
2. oil ring "support rail" or "bridge spacer"
3. oil ring "roll pin locator"
KB uses the roll pin locator method on their hypereutectic pistons. (They use the support rail/bridge spacer on their forged pistons.) The tiny roll pin (.063" or .093") is positioned vertically in the oil ring land and only protrudes halfway into the 3/16" oil ring. The oil ring end gap is then prevented from migrating into the wrist pin bore (top .750" opening). This requires the lower (bottom one only!) oil ring rail (not the expander) to be modified. You must remove .095" (.093" roll pin diameter) from the lower oil ring rail and then obviously position the gap with roll pin locator. (Some KB pistons have a .063" roll pin, so then you would only remove .065" from the end gap. Measure the pin.) Evidently this method doesn't add any weight to the piston assembly and has been very successful. Please read this link to installation instructions using roll pin locator:

If you're using standard stroke engine components, then the roll pin locator procedure above, will not apply to you.

You can use any appropriate size piston ring set, however modification is necessary. These piston ring end gaps and cylinder bore clearance dimensions need to be strickly adhered to.

Where to measure your KB piston for proper piston to wall clearance.


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