MAHLE 42157CP.040 Premium Piston Ring Set 4.040" Bore Plasma-Moly LS Gen III/IV

The MAHLE 42157CP.040 is a premium plasma-moly piston ring set designed for Gen III/IV LS engines with a 4.040" oversize bore. Ring thicknesses are 1.2mm (top), 1.5mm (intermediate), and 2.5mm (oil), and the set is sold as 8 complete cylinder sets. MAHLE is one of the world's largest OE piston ring manufacturers, and this set reflects that engineering pedigree with advanced materials, precise tolerances, and installer-friendly design.

Key Features:

• SAE 9254 high alloy steel base material delivers higher tensile and yield strength, extended fatigue resistance, and increased material hardness
• Patented HV385 thermal spray plasma-moly face coating on top compression rings for superior wear resistance and reduced friction
• Barrel-faced compression ring contact area with CNC-controlled gap chamfer optimizes compression and reduces blowby
• Reverse-twist intermediate (Napier second) rings with taper-face machining provide better groove side sealing and superior oil control
• CP-20 oil ring assemblies feature an exclusive 20-degree ear angle for optimal side sealing against the cylinder wall, plus a chemically polished expander for enhanced oil drainback
• Pre-lapped rings seat immediately upon installation, virtually eliminating traditional break-in time
• Ring tension, materials, and coatings optimized for reduced friction and extended service life

MAHLE piston rings are engineered to OE form, fit, and function, making the 42157CP.040 an ideal choice for engine rebuilds requiring a 4.040" bore on LS-based Gen III/IV V8 platforms. Whether used in a stock rebuild or a performance build, these rings deliver proven durability and easy installation.