MAHLE 41858CP-040 Precision-Ground Performance Piston Ring Set Bore - 4.040 V8

The MAHLE 41858CP-040 is a precision-ground performance piston ring set designed for V8 engines with a 4.040-inch (+.040" oversize) bore. Featuring a three-ring configuration with axial heights of 1.5mm / 1.5mm / 3.0mm, this set is engineered to deliver OE-grade sealing performance, reduced friction, and long-term durability in both street and performance applications.

Key Features:

• Plasma-moly faced upper compression ring (ductile iron base) for superior wear resistance and break-in characteristics under high-heat, high-pressure conditions
• Cast iron lower compression ring with reverse twist design for improved groove-side sealing and taper-race machining to enhance cylinder wall contact
• Stainless steel CP-20 oil control ring assembly with chrome-faced rails and an exclusive 20-degree ear angle for maximum side seal in the oil ring groove and improved oil drain-back
• SAE 9254 high-alloy steel base material providing higher tensile and yield strength, extended fatigue resistance, and increased hardness for performance engine demands
• Barrel-faced compression ring contact area with CNC-controlled gap chamfer to optimize compression sealing and minimize blow-by
• Pre-lapped rings seat immediately upon installation, virtually eliminating extended break-in time
• Foolproof installation design — rings are engineered so they cannot be installed incorrectly
• Sold as a complete set for one 8-cylinder engine

MAHLE is one of the world's largest OE piston ring manufacturers, and the 41858CP-040 reflects that expertise. Ring tension, materials, and coatings are all optimized for reduced friction, minimized oil consumption, and extended service life — making this set an excellent choice for engine rebuilds, overhauls, and re-ring projects.