4.625 Stroke For SE 121 ST & VVT Engines

4.085 Piston Kit fits Screamin’ Eagle® 121 ST & VVT Engines

This is an improved, stronger piston design to fit SE 121 ST & VVT Engines.

Made from 2618 forgings, we added extra strength in this piston with +.070 of added deck material to strengthen this piston over the O.E. Design.  This engineering fix can help prevent any application where the 121 engines has suffered an O.E. piston failure, or use as a preventive action for any severe duty use applications.

Dome volume on this piston provides the same compression as the SE 121 engine; slightly more if you set squish band tighter, we suggest (.038-.042”) depending on the desired RPM scale than the original equipment specification.

This piston kit requires cylinder liners to be professionally sized to the O.E. cylinders for a straighter bore and improved surface finishes with benefits of improved ring seal for increased power and durability.  Kit includes pistons, pins, rings & clips.  https://www.zippersperformance.com/services-2/cylinder-sizing-with-unique-piston-designs/

In addition, you can top off this improvement for your SE 121 engine with a Red Shift 532 cam or the 534 for excellent power across the entire RPM range and many trouble-free miles of enjoyment.   https://www.zippersperformance.com/red-shift-cams-rs532-for-milwaukee-eight-engines/

Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.

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