DSS Racing FX Series Forged Piston Set

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

1-6840-4125C / 2-6840-4125C / 3-6840-4125C / K1-6840-4125C / K2-6840-4125C / K3-6840-4125C

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, this set offers enhanced strength and durability for high-performance and street applications. Ideal for enthusiasts looking to upgrade their engine’s internals, these pistons provide improved reliability under increased boost, higher RPMs, and aggressive driving conditions.

With a 4.125" bore size and a compact flat-top design, these pistons maintain optimal compression ratios while allowing for various combustion chamber volumes. Whether you are building a naturally aspirated or forced induction engine, the DSS Racing FX Series pistons deliver consistent performance and longevity.

Key Features:

Built to meet the demands of modern Mopar Hemi engines, these pistons incorporate advanced design elements for superior operation:

• Compatible with 398 Small Block Mopar Hemi Gen III and FX series engines
• Forged construction for maximum strength and fatigue resistance
• Flat-top piston design with -1.5cc volume for precise compression control
• Pin diameter of .927" with options for full-floating or press-fit installation
• Ring groove dimensions: 1.2mm top and second rings, 3mm oil ring
• Stroke compatibility of 3.720" and connecting rod length of 6.2"
• Available in multiple combustion chamber volumes: 65cc, 74cc, and 85cc
• Approximate compression ratios ranging from 9.52:1 to 11.77:1 depending on chamber size

Construction & Design:

Each piston in the DSS Racing FX Series is forged from high-grade aluminum alloy, providing an excellent balance of lightweight design and structural integrity. The forging process enhances grain structure, resulting in superior resistance to heat and mechanical stress compared to cast pistons. The flat-top design with a slight dish (-1.5cc) optimizes combustion efficiency and reduces the risk of detonation under high-performance conditions.

The pistons feature precision-machined ring grooves to ensure proper ring seating and oil control, contributing to reduced blow-by and improved engine longevity. The wrist pin options allow for either full-floating or press-fit installation, accommodating various engine build preferences and enhancing durability.

Installation & Fitment:

This piston set is designed to fit most Chrysler, Dodge, Jeep, and Ram 6.4L 392 Hemi engines with a 4.125" bore. Installation requires standard engine rebuilding procedures, including proper honing and cleaning of the cylinder bores. Depending on the wrist pin choice, either full-floating or press-fit installation methods can be employed. It is recommended to consult with a professional engine builder to ensure optimal fitment and clearances.

What's Included:

• Set of forged pistons sized for 4.125" bore
• Wrist pins (.927") with options for full-floating or press-fit
• Precision-machined ring grooves for 1.2/1.2/3mm ring sets
• Installation instructions and technical specifications

Ideal For:

This piston set is perfect for Mopar enthusiasts and professional engine builders upgrading or rebuilding 6.4L 392 Hemi engines. It suits naturally aspirated builds, forced induction setups, and high-performance street or track applications where enhanced durability and consistent compression ratios are critical.

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.