MAHLE 3150034-040 Plasma-Moly Ductile Piston Ring Set 4.040 in. Bore 5/64 5/64 3/16

The MAHLE 3150034-040 is a plasma-moly ductile iron piston ring set engineered for the serious performance builder. Designed for an 8-cylinder engine with a 4.040-inch (102.62mm) bore (+0.040" oversize), this complete set delivers maximum combustion sealing and minimal frictional losses for real, measurable power gains on the street, strip, or water.

MAHLE's plasma-moly ductile iron top rings are manufactured from SAE 9254 alloy steel combined with a proprietary plasma face coating to extend service life, eliminate ring breakage, reduce side wear, and minimize groove pound-out. The Reduced Radial Wall (RRW) design allows the top ring groove to be positioned closer to the crown of the piston, reducing crevice volume and unburned fuel while improving the ring's ability to conform to cylinder bore distortion found in high-output, high-RPM engines.

Key Features:

• Bore Size: 4.040 in. (102.62mm) — +0.040" oversize
• Ring Widths: 5/64 in. top / 5/64 in. second / 3/16 in. oil
• Sold as: Complete set for one 8-cylinder engine (8 sets total)
• Top Ring: Ductile iron, plasma-moly face coating, barrel-face profile for instant break-in and consistent cylinder wall contact
• Second Ring: Napier THG (Tapered Hook Groove) design acts as a check valve to relieve combustion pressure under the top ring and provides superior oil control
• Oil Ring: CP-20 three-piece oil control ring with exclusive 20-degree ear angle for maximum cylinder wall seal and reduced tension
• Reduced Radial Wall (RRW): Allows higher ring placement on the piston for reduced crevice volume and improved thermal efficiency
• Standard tension — compatible with street, racing, and marine applications
• Precision-ground ring flanks for maximum ring-to-groove sealing

MAHLE is the world's largest piston ring manufacturer, with over a century of OE and aftermarket engineering experience. The 3150034-040 ring set reflects that heritage, offering race-proven performance backed by simulation-driven design tools that have been validated on dynamometers and racetracks worldwide.