MAHLE 3021231 Performance Napier Steel 2nd Ring Set 4.270in x 1.0mm .136in RW Plain

The MAHLE 3021231 is a Performance Napier Steel Second Ring Set designed for high-performance and racing engine builds. This file-fit ring set features a 4.270-inch bore diameter, 1.0mm ring width, and .136-inch radial wall (RW) with a plain finish, making it an ideal choice for builders pairing these rings with custom or forged performance pistons.

MAHLE's steel Napier second ring is engineered to serve as a check valve, relieving excessive combustion pressure buildup beneath the top ring. This prevents top ring float, maintains the combustion seal, and reduces power loss — critical advantages in high-output and forced-induction applications.

Key Features:

• Bore Size: 4.270 inches
• Ring Width: 1.0mm
• Radial Wall: .136 inches
• Ring Type: Napier Steel Second Ring (2nd Ring)
• Finish: Plain
• Ring Set: Performance file-fit design for custom gap setup
• Steel Napier profile provides superior oil control — managing up to 80% of oil scraping duty
• Acts as a combustion pressure check valve to stabilize the top ring and preserve sealing
• Engineered using MAHLE's piston ring simulation and computer development tools to minimize friction and maximize power
• Precision-finished flanks for optimal ring-to-piston groove sealing

MAHLE is the world's largest piston ring manufacturer, with over a century of experience supplying original equipment and aftermarket rings to the world's leading engine builders. The 3021231 second ring set is sold as a performance component intended for use by experienced engine builders who will file-fit the rings to their specific bore and application requirements.