Product Description
Genuine Cummins
Cummins 3904408 — Valve Stem Guide (Intake, Thick-Wall 60.50 mm) for B-Series
MPN: 3904408 | Also Known As: valve guide, intake valve stem guide | For: Cummins B-Series (4BT/6BT), primarily 5.9L 12V applications
Why This Part
- ✓ OE geometry for precise valve stem alignment and smooth motion.
- ✓ Thick-wall intake guide (60.50 mm length) for durability in heavy-duty use.
- ✓ Direct-fit for B-Series cylinder heads; restore proper valve-to-guide clearance.
- ✓ Genuine Cummins quality for long service life.
OE Fit Intake Guide B-Series
Quick Specs
| Type | Valve stem guide (intake) |
|---|---|
| OE Part # | 3904408 |
| Length / Style | 60.50 mm thick-wall |
| Qty per Engine | Varies; typically intake positions on 6BT 12V (order by cylinder head build) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1998 | 5.9L 12-Valve 6BT (B-Series) | Ram 2500/3500 |
Industrial/Off-Highway: Common on 4BT/6BT B-Series industrial builds; always confirm by ESN and cylinder head casting.
Often Paired With
- Exhaust Valve Guide: Cummins 3904409 (approx. 51.75 mm)
- Valve Stem Seals (intake & exhaust, by head casting)
- Cylinder Head: common casting 3920487 (verify by ESN)
What’s In The Box
- (1) Genuine Cummins Valve Stem Guide (3904408) — intake
- Other guides/seals sold separately (see “Often Paired With”).
Install Tips
- Press old guides out with correct tooling; chill new guides and warm head per service manual.
- After install, ream/hone to spec and verify stem-to-guide clearance.
- Always use new valve stem seals and check seat concentricity after guide service.
FAQ
IS 3904408 THE INTAKE OR EXHAUST GUIDE?3904408 is the intake guide (thick-wall, ~60.50 mm). The common exhaust companion is 3904409 (~51.75 mm).
WILL THIS FIT MY 1989–1998 5.9L 12V RAM?Yes—this valve guide is used on B-Series 6BT 12-valve applications (verify by ESN/cylinder head casting).
IS THIS A GENUINE CUMMINS PART?Yes—this listing is for an OE Cummins valve stem guide (3904408).
DO I NEED MACHINE WORK AFTER INSTALLATION?Yes—guides typically require reaming/honing to spec and valve seat touch-up for correct stem clearance and sealing.
WHAT CYLINDER HEAD CASTINGS DOES THIS WORK WITH?Commonly used with heads like casting 3920487 on 6BT; verify by ESN and casting before ordering.
