MAHLE 1979648 Oil Ring Support Rail Bore - 4.145-4.160 2mm

The MAHLE 1979648 is an oil ring support rail designed for performance engine builds with cylinder bore sizes ranging from 4.145 to 4.160 inches. This 2mm support rail is a critical component used with MAHLE pistons that feature reduced radial wall thickness in the oil ring groove.

Key Features:

• Fits bore sizes from 4.145 to 4.160 inches
• 2mm thickness specification
• Prevents piston rotation for improved cylinder seal
• Minimizes friction and maximizes ring sealing efficiency
• Ensures proper gas pressure delivery to rings at high RPM
• Installs at the bottom of the oil ring groove

Oil ring support rails are used in high-performance piston applications where the wrist pin bore extends into the ring land area. The support rail sits in the bottom of the oil ring groove with its dimple positioned down into the gap created by the pin bore, preventing rotation while the oil ring assembly stacks above it. This design maintains proper ring support and sealing even with the compromised groove structure caused by the high pin placement common in performance pistons.

Installation Note: The support rail should fit tight to the back wall of the oil ring groove and must not overlap when properly installed on the piston. It should never contact the cylinder wall.