MAHLE 42157CP.030 Premium Plasma-Moly Piston Ring Set 4.030 in. Bore V8

The MAHLE 42157CP.030 is a premium plasma-moly piston ring set engineered for V8 engines with a 4.030-inch (102.362mm) bore at a 0.030-inch oversize.

MAHLE piston rings are constructed from an SAE 9254 high alloy steel base material, delivering superior tensile and yield strength, extended fatigue resistance, and increased material hardness. Combined with MAHLE's proprietary HV385 thermal spray plasma-moly face coating, these rings represent the highest level of piston ring technology available for the OE replacement market.

Ring Dimensions:

• Top (compression) ring: 1.2mm height, 0.151 in. radial width — barrel-faced contact area for more efficient compression
• Second (intermediate) ring: 1.5mm height, 0.169 in. radial width — reverse twist design for superior groove side sealing with taper race machining
• Oil control ring: 2.5mm height, 0.110 in. radial width — CP-20 assembly with exclusive 20-degree ear angle

Key Features:

• Pre-lapped finish seats immediately, virtually eliminating engine break-in time
• Ring materials, coatings, and tension optimized per application for reduced friction and extended service life
• CNC-controlled gap chamfer on compression rings optimizes compression and reduces blow-by
• CP-20 oil ring assemblies feature an exclusive 20-degree ear angle for best-in-class cylinder wall side sealing
• Special chemical polish on the oil ring expander enhances oil drain-back performance
• SAE 9254 Napier-design second rings provide superior oil control and combustion gas management
• Designed with OE form, fit, and function for reliable, repeatable installation

MAHLE is one of the world's largest OE piston ring manufacturers, supplying over 100,000 OE and aftermarket part numbers globally. The 42157CP.030 delivers the installer-friendly design and engineering precision that professional engine builders rely on.