Product Description
Genuine Cummins
Cummins 3800785 — Engine Piston Kit (.040" / 1.00 mm Oversize)
MPN: 3800785 | Also Known As: piston & ring kit, oversize piston kit | Intended Use: Tier 2 ISB/QSB 5.9L; automotive 1998.5–2002 Ram 5.9L 24V rebuilds
Why This Part
- ✓ OE-spec oversize piston kit for common machine-shop overbores: .040" (1.00 mm).
- ✓ Complete single-cylinder kit: piston, ring set, wrist pin, and pin retainers (order qty 6 for a full engine).
- ✓ Designed for ISB 5.9L 24V VP44 (1998.5–2002) rebuilds; restores compression & oil control.
- ✓ Durable OE materials and profiles for long service life.
.040" Oversize Order 6 for Full Set OE Geometry
Quick Specs
| Type | Engine piston kit (.040" / 1.00 mm) |
|---|---|
| OE Part # | 3800785 |
| Includes | Piston, ring set, wrist pin, pin retainers |
| Qty Required | 6 per engine (sold individually) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1998.5–2002 | Ram 5.9L ISB 24V (VP44) | Ram 2500/3500 |
Industrial/Off-Highway: Used primarily on Tier 2 5.9L ISB/QSB—verify by ESN before ordering.
Often Paired With
- Head gasket set & head bolts (one-time torque-to-yield, replace on rebuild)
- Main & rod bearings matched to crank journals
- Ring compressor sized for .040" overbore
- Cross-hatch hone & cleanliness per machine shop spec
What’s In The Box
- (1) Cummins Piston (.040"/1.00 mm)
- (1) Piston Ring Set (.040"/1.00 mm)
- (1) Wrist Pin
- (2) Pin Retainers (circlips)
Install Tips
- Confirm cylinder overbore and piston-to-wall clearance per spec; measure with micrometer/boring bar reports.
- File-fit rings if required; verify end gaps by cylinder.
- Orient ring gaps and piston correctly; lubricate during assembly.
- Always check deck height, piston protrusion, and valve-to-piston clearance with your cam profile.
FAQ
IS THIS THE .040" (1.00 MM) OVERSIZE KIT?Yes—3800785 is the .040" / 1.00 mm oversize piston kit.
WHAT DOES A SINGLE-CYLINDER KIT INCLUDE?Piston, rings, wrist pin, and pin retainers. Order qty 6 for a full engine.
WHAT YEARS/TRUCKS DOES THIS COVER?Designed for 1998.5–2002 Ram 2500/3500 with the 5.9L ISB 24V VP44. For industrial engines, verify by ESN.
IS THIS A GENUINE CUMMINS KIT?Yes—this is an OE Cummins piston kit matched to ISB/QSB 5.9 applications.
DOES CUMMINS LIST TIER/APPLICATION INFO?Yes—Cummins notes 3800785 is used primarily on Tier 2 5.9L ISB/QSB engines.
