MAHLE 4380MS Plasma-Moly Performance Piston Ring Set 4.375" File Fit 1/16" 1/16" 3/16"

The MAHLE 4380MS is a performance plasma-moly piston ring set designed for a 4.375-inch bore (4.380" with +.005" oversize), featuring a file-fit design and standard-tension oil rings.

MAHLE's advanced piston ring simulation and computer-aided development process produces rings that deliver measurable horsepower gains through friction reduction — results that show up on the dyno and on the track. Ultra-flat ring flanks ensure optimal ring-to-piston groove sealing for maximum combustion efficiency.

Ring Construction Details:

• Top Ring: Ductile iron, positive-twist, barrel-face design with plasma-moly inlay for superior wear resistance and scuff protection
• Second Ring: Cast iron, reverse-twist, tapered-face configuration — acts as a check valve to relieve combustion pressure buildup beneath the top ring, improving top ring stability and sealing
• Oil Ring: 3-piece standard-tension assembly for reliable, consistent oil control

Key Specifications:

• Bore Size: 4.375" nominal (+.005" oversize = 4.380" bore)
• Ring Thickness: 1/16" (top), 1/16" (second), 3/16" (oil)
• Fit Type: File Fit — requires end-gap filing to match your specific application
• Oil Ring Tension: Standard

The file-fit design gives engine builders precise control over ring end gap, making the MAHLE 4380MS ideal for performance builds where exact tolerances are required. Compatible with a wide range of V8 performance pistons using the traditional 1/16", 1/16", 3/16" ring groove configuration.