Carrillo CPN-3740 CPN High-Performance Piston Ring Set 3.740in Bore

The CP-Carrillo CPN-3740 is a high-performance piston ring set engineered for 3.740-inch bore applications. Designed to deliver maximum cylinder sealing with minimum friction, this CPN-series ring set is purpose-built for high-cylinder-pressure engines including sport compact, small-bore, and performance builds.

Ring Set Composition:

• Top Ring: Steel compression ring with gas nitriding treatment — compatible with both Nikasil and cast iron cylinder bores, providing exceptional durability and reduced friction
• Second Ring: Cast iron with a taper underhook groove (Napier) face — acts as a wiper to push oil away from the combustion chamber and allows use of a lower-tension oil ring
• Oil Ring: Two-piece design featuring gas nitrided rails paired with a low-tension expander and mini-flex vent design for reduced cylinder wall drag

Key Features:

• 3.740-inch (94.996mm) bore diameter
• High-strength, low-tension ring package engineered for high cylinder pressures
• Gas nitrided top ring compatible with Nikasil and cast iron bores
• Mini-flex vent oil ring design reduces friction for improved power output
• Sold as one complete ring set for one piston
• A spec sheet with ring end gap recommendations is included

CP-Carrillo recommends plateau honing the cylinder bore with a crosshatch angle of 35–40 degrees prior to installation for optimal ring seal. Always verify ring end gap before installation, as correct gap varies by application and power configuration. OEM rings are not a substitute for this ring set when used with CP-Carrillo pistons.