DSS Racing FX Series Forged Piston Set

Fits Chrysler / Dodge / Jeep / Ram 6.4L 392 Models

1-6840-4090C / 2-6840-4090C / 3-6840-4090C / K1-6840-4090C / K2-6840-4090C / K3-6840-4090C

Overview:

The DSS Racing Gen III Hemi FX Series Forged Piston Set is engineered specifically for the Chrysler, Dodge, Jeep, and Ram 6.4L 392 engines. Designed to replace factory pistons in the 391 Small Block Mopar Hemi Gen III platform, these pistons offer enhanced strength and durability for high-performance applications. Ideal for enthusiasts and professional builders seeking reliable, forged pistons that maintain factory bore size while improving engine resilience under demanding conditions.

With a 4.090" bore size and a compact flat-top design, these pistons optimize combustion efficiency and compression ratios, supporting both street and track performance. The set is compatible with full-floating or press-fit wrist pins, allowing flexibility in assembly preferences.

Key Features:

These forged pistons incorporate advanced design elements to ensure superior performance and longevity:

• Precision forged construction for maximum strength and fatigue resistance
• 1.21" compression height tailored for Gen III Hemi 6.4L 392 engines
• 1.5cc flat-top piston crown for optimized combustion chamber volume
• .927" wrist pin diameter compatible with full-floating or press-fit configurations
• Ring groove dimensions: 1.2mm top and second rings, 3mm oil ring for effective sealing
• Designed for a 3.720" stroke and 6.2" connecting rods, matching factory specifications
• Available in multiple combustion chamber volumes (65cc, 74cc, 85cc) to achieve compression ratios from 9.38:1 up to 11.6:1
• Compatible with most Chrysler, Dodge, Jeep, and Ram 6.4L 392 engines for direct fitment

Construction & Design:

DSS Racing utilizes high-grade forged aluminum alloy to manufacture these pistons, ensuring exceptional strength-to-weight ratio and thermal conductivity. The forging process refines the metal grain structure, enhancing durability and resistance to cracking under high cylinder pressures. The flat-top design with a slight volume reduction (-1.5cc) optimizes combustion efficiency and power output while maintaining a reliable compression ratio.

The pistons feature precision-machined ring grooves and skirt profiles to reduce friction and wear, contributing to improved engine longevity. The wrist pin bore is engineered for compatibility with both full-floating and press-fit pins, providing versatility during engine assembly.

Installation & Fitment:

This piston set is designed for direct replacement in most Chrysler, Dodge, Jeep, and Ram 6.4L 392 engines using a 4.090" bore. Installation requires standard engine rebuild procedures, including proper honing and cleaning of the cylinder bores. The pistons fit factory stroke and rod dimensions, minimizing the need for additional modifications. Builders should verify ring end gaps and wrist pin fitment based on their specific engine build and assembly preferences.

What's Included:

• Set of forged pistons sized for 4.090" bore
• Compatible with full-floating or press-fit wrist pins (pins not included)
• Precision-machined ring grooves ready for ring installation

Ideal For:

This piston set is ideal for performance enthusiasts, engine builders, and racers upgrading or rebuilding Chrysler, Dodge, Jeep, or Ram 6.4L 392 Hemi engines. It suits applications ranging from street performance to moderate track use where enhanced piston strength and durability are required without altering factory bore size or stroke. These pistons provide a solid foundation for increased power and reliability in naturally aspirated or mildly boosted setups.

DSS Racing — Founded in 1983 originally as Danny’s Speed Shop, DSS Racing has grown from a small Midwest performance engine shop into a respected name in forged engine components for the high-performance and racing markets. Based in St. Charles, Illinois, DSS is best known for its forged pistons and machined engine parts made in the USA that have been used in championship engines and thousands of builds, blending old-school racing roots with precision manufacturing for enthusiasts and racers alike.