Product Description
Cummins 4089671 — Engine Piston Kit, 1.00 mm (.040") Oversize
MPN: 4089671 | Also Known As: .040" over piston kit, 1.00 mm overbore kit | Related Sizes: 4089669 (STD), 4089670 (.020"/0.50 mm)
Why This Part
- ✓ OE piston kit engineered for 5.9L ISB durability and correct compression.
- ✓ 1.00 mm (.040") oversize for professionally bored/honed blocks.
- ✓ Complete per-cylinder kit to simplify rebuild parts selection.
- ✓ Genuine Cummins quality for long service life and reliable sealing.
Quick Specs
| Type | Engine piston kit (per cylinder) |
|---|---|
| Overbore Size | 1.00 mm (.040") |
| OE Part # | 4089671 |
| Typical Kit Contents | Piston, matched oversize ring set, wrist pin, (2) pin retainers |
| Qty Required | 6 kits per engine (sold individually) |
Contents based on standard Cummins kit configuration; verify by ESN if needed.
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2004.5–2007 | Ram 5.9L ISB (24V Common-Rail) | Ram 2500/3500 |
Industrial/Off-Highway: Used primarily on non-certified ISB/QSB 5.9 applications—verify by ESN before ordering.
Often Paired With
- Piston kits (all 6 cylinders): order quantity 6 for a full set
- Main & rod bearings: Clevite/Interstate-McBee sets (size to crank)
- Full gasket set & head bolts/studs: OE or ARP (use torque plate when honing)
- Oil cooler & gaskets: 3959031 (5.9L) with proper seals
What’s In The Box
- (1) Cummins 1.00 mm (.040") Oversize Piston Kit (see contents above)
Install Tips
- Bore & hone with a torque plate to final size; confirm piston-to-wall clearance.
- Measure & file ring end gaps to spec; verify ring orientation and groove clearance.
- Check piston protrusion vs. head gasket thickness; follow Cummins service procedures.
FAQ
WILL THIS FIT MY 2004.5–2007 5.9L CUMMINS RAM?Yes—4089671 is specified for 2004.5–2007 5.9L ISB (24V common-rail). Always verify by VIN/ESN before purchase.
WHAT DOES “1.00 MM (.040") OVER” MEAN?The cylinders must be bored and honed 1.00 mm over standard. This compensates for wear/damage and restores roundness and finish.
WHAT’S INCLUDED—DOES IT COME WITH RINGS?Per-cylinder kit typically includes the piston, matched oversize ring set, wrist pin, and pin retainers. Verify by ESN if you need to confirm contents.
HOW MANY KITS DO I NEED?Six (6) kits for a complete engine—one per cylinder.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins piston kit for proper fit, metallurgy, and performance.
