Product Description
Genuine Cummins
Cummins 4089670 — Engine Piston Kit (.50mm / .020 Over) for ISB 5.9L
MPN: 4089670 | Also Known As: piston assembly kit, .020 over piston kit | Oversize: 0.50 mm (.020") | Includes: piston, wrist pin, pin clips, and ring set
Why This Part
- ✓ OE materials & geometry for proper compression and oil control.
- ✓ Matched rings for the oversize to restore sealing after machine work.
- ✓ Direct-fit for the correct ISB 5.9L applications when bored/honed to .020" over.
- ✓ Durable construction built to Cummins specifications.
.020" Over OE Kit Sold Individually (6/engine)
Quick Specs
| Type | Engine piston kit (piston + rings + pin + clips) |
|---|---|
| OE Part # | 4089670 |
| Bore Size | 0.50 mm (.020") oversize — requires machine work |
| Qty Required | 6 per engine (sold individually) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2004.5–2007 | Ram 5.9L ISB (24V Common-Rail) | Ram 2500/3500 |
Industrial/Off-Highway: Common on ISB/QSB 5.9 applications; verify by ESN/CPL. Oversize requires machining.
Often Paired With
- Main & rod bearing sets (match to crank journal size)
- Complete gasket set (upper & lower) for rebuild
- Head bolts or studs and new oil & filter at first start
- Machine shop services: bore & hone to .020" over, deck & hone as needed
What’s In The Box
- (1) Cummins Engine Piston Kit 0.50 mm (.020") Over — piston, rings, wrist pin, and circlips
- Order 6 kits for a complete engine set
Install Tips
- Have cylinders measured and bored/honed to .020" over; confirm piston-to-wall and ring end gaps.
- Match pistons by ESN/CPL when mixing components; verify bowl/compression spec per service manual.
- Cleanliness is critical; pre-lube, verify bearing clearances, and follow torque sequences.
FAQ
WILL THIS FIT MY 2004.5–2007 5.9L CUMMINS RAM?Yes—this .020" over piston kit is listed for 2004.5–2007 Ram 2500/3500 with the 5.9L ISB common-rail (verify by VIN/ESN/CPL).
DOES THE KIT INCLUDE RINGS?Yes—the Cummins piston kit includes the matched ring set along with the piston, wrist pin, and clips.
HOW MANY KITS DO I NEED?Order 6 kits to service all cylinders on a 5.9L inline-6 (kits are sold individually).
DO I NEED MACHINE WORK FOR .020" OVER?Yes—.020" over requires a professional bore and hone. Always confirm piston-to-wall and ring end gap to spec.
IS THIS AN OEM CUMMINS PART?Yes—OE Cummins part number 4089670.
