Product Description
CUMMINS 4089670 OEM ENGINE PISTON KIT (.020 OVER) – RAM 5.9L (2004.5–2007)
The genuine CUMMINS 4089670 OEM .020 over piston kit is the factory-engineered oversize piston assembly designed for professional engine rebuilds on 2004.5–2007 5.9L Cummins ISB engines. When cylinders are worn, scored, or tapered, machining the bores and installing an oversized OEM piston restores compression, sealing efficiency, and long-term durability.
This kit includes the correct oversize piston, wrist pin, piston rings, and retainers—each built to Cummins metallurgy, coating, and tolerance specifications. Whether you're rebuilding a high-mileage work truck or restoring a performance build back to factory health, choosing an OE Cummins piston ensuring exact fitment and reliability is essential.
Key Features
- Genuine Cummins OEM oversize piston kit – not aftermarket.
- .020 over size for machined cylinders requiring oversize pistons.
- Includes piston, rings, pin, and retainers for a complete rebuild-ready assembly.
- Engineered to Cummins heat and load specifications for long-term durability.
- Matched machining tolerances ensure correct compression and ring sealing.
Fitment Details
- Engine: Cummins 5.9L ISB (Common Rail)
- Years: 2004.5–2007
- Applications: Dodge/Ram 2500 & 3500, plus ISB industrial/commercial variants
- Notes: Requires machined cylinder bores to .020 over specification. Always measure and verify.
Cross-Reference & Companion Cummins Parts
For a complete engine overhaul, pair CUMMINS 4089670 with other genuine Cummins components available at CPP Diesel:
- CUMMINS 4981790 VALVE STEM SEAL – 5.9 / 6.7
- CUMMINS 3944083 VALVE LOCK – 5.9 / 6.7
- VIEW ALL GENUINE CUMMINS OEM PARTS
Common Cummins references: 4089670 (.020), 4089669 (.010), 4089671 (.040) — verify by VIN/ESN and machine shop measurement.
Installation Notes
- Cylinder bores must be machined to the correct oversize (+.020").
- Always measure piston-to-wall clearance per Cummins specifications.
- Use proper ring end-gap orientation and verify end-gap after honing.
- Lubricate wrist pin and rings during assembly.
- Balance rotating assembly when replacing one or more pistons.
Specifications for cummins 4089670
| Attribute | Value |
|---|---|
| Brand | Cummins (Genuine OEM) |
| Cummins Part Number | 4089670 |
| Oversize | .020" (0.50mm) over standard |
| Included Components | Piston, wrist pin, piston rings, retainers |
| Engine Compatibility | 5.9L Cummins ISB (2004.5–2007) |
| Vehicle Fitment | Ram 2500 / 3500, plus ISB-equipped commercial variants |
| UPC | 190910384828 |
| GTIN | 190910384828 |
| Shipping Weight | Approx. 2.8 lbs |
| Shipping Method | Standard ground; heavy-duty packaging |
| E-Codes / Emissions | Non-emissions internal engine component |
| Prop 65 Warning | WARNING: This product may expose you to chemicals known to the State of California to cause cancer or reproductive harm. See www.P65Warnings.ca.gov. |
| Country of Origin | As labeled by Cummins (varies by batch) |
Frequently Asked Questions
WILL THIS .020 OVER PISTON FIT MY 5.9L CUMMINS?
Yes, as long as your engine is a 2004.5–2007 5.9L ISB and the cylinder bores have been machined to .020 over. Always confirm with your machine shop.
DOES THIS KIT INCLUDE RINGS AND THE WRIST PIN?
Yes, the CUMMINS 4089670 kit includes the piston, rings, wrist pin, and retainers—everything required for installation.
CAN I INSTALL OVERSIZE PISTONS WITHOUT MACHINING?
No. Oversize pistons require the cylinder to be bored/honed to the correct oversize specification.
SHOULD I REPLACE ALL SIX PISTONS?
It is strongly recommended to maintain engine balance, performance, and longevity.
ARE THESE GENUINE CUMMINS PARTS?
Yes — CPP Diesel supplies only authentic Cummins OEM piston kits for maximum reliability.
