Product Description
Genuine Cummins
Cummins 3904105 — Exhaust Valve Seat / Valve Insert (B-Series)
MPN: 3904105 | Also Known As: exhaust valve seat, valve insert | Counterpart (Intake): 3906854
Why This Part
- ✓ OE seating surface for proper exhaust valve seal and heat transfer.
- ✓ Direct-fit for B-Series heads used on 5.9L 12-valve 6BT (1989–1998) and many 4BT/industrial applications.
- ✓ Restores compression & durability when seats are worn, pitted, or recessed.
- ✓ Sold individually—6 required per engine for the exhaust side (12 total seats w/ intakes).
OE Fit Machine Install Exhaust Side
Quick Specs
| Type | Valve seat insert — Exhaust |
|---|---|
| OE Part # | 3904105 (exhaust) | Intake counterpart: 3906854 |
| Quantity | 6 req’d per engine (exhaust); 12 total seats with intakes |
| Applications | Cummins B-Series (4BT/6BT); automotive 5.9L 12-valve Ram (see fitment) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1998 | 5.9L 12-Valve 6BT (VE & P-pump) | Dodge Ram 2500/3500 |
Industrial/Off-Highway: Common on 3.9L 4BT/5.9L 6BT B-Series engines in equipment/generator sets—verify by ESN before ordering.
Often Paired With
- Intake Valve Seat: Cummins 3906854 (6 req’d)
- Valve Guides: 3904408 (60.5 mm), 3904409 (51.75 mm)
- Exhaust/Intake Valves: OE 12-valve replacements
What’s In The Box
- (1) Genuine Cummins Exhaust Valve Seat / Insert (3904105)
- Machine work, valves, and guides sold separately.
Install Tips
- Professional machine-shop installation recommended (press-fit with correct interference).
- After install, cut the seat angles, verify concentricity & seat width, and set installed height per service manual.
- Replace worn valves/guides; check recession and lash after initial run-in.
FAQ
WILL THIS FIT MY 1989–1998 5.9L 12-VALVE RAM?Yes—3904105 is the OE exhaust valve seat for B-Series heads used on 1989–1998 5.9L 12-valve 6BT (verify by ESN).
HOW MANY DO I NEED?Six (6) for the exhaust side per engine. Pair with six (6) intake seats 3906854 for a full set of twelve.
IS THIS AN OEM CUMMINS PART?Yes—this is a genuine Cummins valve insert/seat (3904105) for exhaust valves.
DOES THIS FIT 24-VALVE OR COMMON-RAIL ENGINES?This listing targets 12-valve heads. Later 24-valve/common-rail heads use different seat part numbers—confirm by ESN.
CAN I INSTALL THESE WITHOUT MACHINE WORK?No—correct press fit and seat machining are required. Have a qualified machine shop perform the work.
