Wiseco 3940H Pro Tru Plasma Moly Piston Ring Set 3.940 in. Bore

The Wiseco 3940H is a high-performance plasma moly piston ring set designed for a 3.940-inch bore. Sold as a single-cylinder set (fits one piston), this ring set is part of Wiseco's Pro Tru lineup — an excellent choice for performance engine builds that demand reliable sealing and long service life without breaking the budget.

Ring Set Options by Application:

• Pro Tru (Plasma Moly): Pre-gapped plasma moly ring set engineered for budget-conscious performance builds; ideal for naturally aspirated street and mild performance applications
• Sport Compact (NPR XX): Includes premium steel nitrided top rings and Napier-style second rings for enhanced sealing and wear resistance
• Late Model EFI / Small Block Chevy: Designed around a 1.2mm steel nitride top ring and Napier GFX second ring for tight tolerances found in modern fuel-injected engines
• Big Block Applications: Many big block configurations utilize a .043-inch back-cut top ring, providing additional material thickness in the area of the intake valve for improved durability

Key Features:

• Plasma moly top ring for superior cylinder wall seal and reduced break-in time
• Pre-gapped design simplifies installation
• Single-piston ring set — covers one cylinder
• Engineered to Wiseco's exacting tolerances for use with Wiseco pistons
• Available ring groove widths: 1/16 in. top, 1/16 in. second, 3/16 in. oil

Wiseco piston ring sets are developed and tested specifically to work with Wiseco pistons, ensuring proper end gap, side clearance, and sealing performance across a wide range of street and competition applications.