Product Description
Cummins 3800785 OEM Engine Piston Kit – ISB 5.9L 24V (1998.5–2002) – .040" Oversize
The Cummins 3800785 OEM Engine Piston Kit is a genuine Cummins .040-inch (1.00mm) oversize piston assembly engineered specifically for 1998.5–2002 ISB 5.9L 24-valve diesel engines. Designed for engines requiring a .040-inch overbore during rebuilding, this kit delivers the exact OE fit, combustion characteristics, durability, and reliability expected from genuine Cummins components. The kit includes the piston, piston rings, wrist pin, and retainers needed for a complete single-cylinder rebuild.
Whether you're restoring compression, repairing cylinder wall damage, or completing a full engine overhaul, the Cummins 3800785 piston kit provides the factory-engineered solution required to maintain proper piston-to-wall clearance, ring sealing, and long-term performance. Unlike many aftermarket alternatives, genuine Cummins pistons maintain OE metallurgy, heat resistance, and combustion bowl geometry for dependable operation under heavy-duty conditions.
Features
- Genuine Cummins OEM piston kit
- .040 Inch (1.00mm) oversize piston
- Designed for rebored engine cylinders
- Includes piston, rings, wrist pin, and retainers
- OE combustion bowl design for proper fuel spray pattern
- Factory-engineered metallurgy and heat resistance
- Restores compression and oil control
- Ideal for engine overhauls and rebuilds
- Designed for long service life and durability
- Direct replacement for Cummins ISB 5.9L 24V applications
Fitment
- 1998.5–2002 Dodge Ram 2500
- 1998.5–2002 Dodge Ram 3500
- Cummins ISB 5.9L 24-Valve Engines
- VP44 Equipped 5.9L Cummins Engines
- Select Tier 2 ISB and QSB Industrial Applications
Note: This piston kit is designed for engines that have been machined .040 inch (1.00mm) over standard bore size. Always verify engine serial number (ESN), bore dimensions, piston-to-wall clearance, and machine shop specifications before installation.
What's Included
- (1) Genuine Cummins .040" Oversize Piston
- (1) Piston Ring Set
- (1) Wrist Pin
- (2) Piston Pin Retainers
Specifications
- Manufacturer: Cummins
- Part Number: 3800785
- Product Type: OEM Engine Piston Kit
- Oversize: .040 Inch (1.00mm)
- Engine Compatibility: ISB 5.9L 24-Valve
- Model Years: 1998.5–2002
- Includes: Piston, Rings, Wrist Pin, Retainers
- Application: Engine Rebuild and Overhaul
- Quantity Required Per Engine: 6 Kit
- Engine Family: ISB / QSB 5.9L
- Bore Requirement: .040 Inch Overbore
- OEM Genuine Part: Yes
Cross Reference Numbers
3800785, Cummins 3800785, 3802006, 3802008, 3800791, 3806203, 3920691
FAQ
Is the Cummins 3800785 piston kit a genuine OEM Cummins part?
Yes. The 3800785 is a genuine Cummins OEM piston kit designed specifically for ISB and QSB 5.9L applications.
What does the .040-inch oversize specification mean?
This piston is designed for cylinders that have been bored and honed .040 inch (1.00mm) larger than the original factory bore size during engine rebuilding.
Does this kit include piston rings and wrist pins?
Yes. The kit includes the piston, ring set, wrist pin, and pin retainers required for one cylinder assembly.
How many piston kits are required for a complete engine rebuild?
The Cummins ISB 5.9L engine uses six cylinders, so six piston kits are required for a complete engine overhaul.
Will this fit all 5.9L Cummins engines?
No. This piston kit is specifically intended for 1998.5–2002 ISB 5.9L 24-valve engines and select QSB applications. Always verify compatibility using your engine serial number (ESN).
What are the related oversize options?
Related Cummins piston kits include 3802006 (standard bore), 3802008 (.020-inch oversize), and 3800791 (.060-inch oversize).
