Product Descreiption
1. Product Specifications
- Part Number: 3942749 (Cross-reference: 3964713, 5253888)
- Applicable Engines: Cummins 6CT8.3, QSC8.3, QSL9, ISL 8.9L diesel engines
- Material: High-strength forged steel / ductile iron, heat-treated for wear resistance and durability
- Type: Exhaust rocker arm (lever-style, single-arm)
- Key Dimensions (Typical):
- Bore diameter (for rocker shaft): Approx. 22 mm
- Valve stem contact end: Rounded, hardened surface
- Pushrod contact end: Screw-adjustable ball socket for valve lash setting
- Weight: Approx. 1.2–1.5 kg
- Condition: 100% new OEM/aftermarket replacement
- Warranty: 1 year
- 2. Installation Position
- Location: Mounted on the cylinder head of the engine, inside the rocker arm housing (valve cover area).
- Mounting: Pivots on a rocker shaft (common shaft for all rocker arms).
- End Connections:
- One end: Contacts the exhaust valve stem tip.
- Other end: Actuated by a pushrod (from the camshaft lifter).
- Orientation: Positioned above the exhaust valves; in Cummins QSC/ISL engines, it is the shorter rocker arm (distinct from the longer intake rocker arm).
- 3. Function
- Core Role: A lever in the valvetrain that transfers and amplifies motion from the camshaft to the exhaust valves.
- Working Principle:
- The camshaft rotates, lifting a pushrod upward.
- The pushrod pushes one end of the rocker arm, which pivots on the rocker shaft.
- The opposite end presses down on the exhaust valve stem, opening the exhaust valve against spring pressure.
- As the camshaft rotates further, the pushrod lowers; the valve spring closes the exhaust valve, and the rocker arm returns to its rest position.
- Key Functions:Timed Exhaust Gas Release: Opens exhaust valves at the correct moment in the 4-stroke cycle to expel burned gases from combustion chambers. Motion Conversion: Converts the camshaft’s rotational motion into linear (up/down) valve motion. Leverage Amplification: Increases cam lift to achieve sufficient exhaust valve opening (lift) for optimal flow. Valve Lash Adjustment: Equipped with an adjustment screw to set and maintain proper clearance (lash) between the rocker arm and valve stem.
