Product Description
Cummins 3904409 — Valve Stem Guide (51.75 mm) for B-Series
MPN: 3904409 | Also Known As: valve guide, exhaust valve stem guide | Cross-Refs: PAI 192040, Interstate-McBee M-3904409, Cummins 4090327
Why This Part
- ✓ OE guide geometry maintains valve-to-seat alignment for proper sealing.
- ✓ 51.75 mm length guide widely used on B-Series heads (4B/6B/6BT).
- ✓ Durable metallurgy to resist wear and valve wobble over high mileage.
- ✓ Ideal for cylinder head refresh with new valves and stem seals.
Quick Specs
| Type | Valve stem guide (commonly used on exhaust positions) |
|---|---|
| OE Part # | 3904409 |
| Length | 51.75 mm (~2.041") |
| Bore / OD (ref.) | ~0.316" I.D. × ~0.554" O.D. (verify during machine setup) |
| Typical Qty | 12-valve head uses 12 guides total; 3904409 commonly used for 6 exhaust guides (confirm head BOM) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1998 | 5.9L Cummins 12-Valve (6BT) | Ram 2500/3500 |
Industrial/Off-Highway: Used primarily on B-Series (4B/6B/6BT/ISB/QSB) heads; verify by ESN and cylinder head P/N before ordering.
Often Paired With
- Valve stem seals (intake & exhaust)
- Valves (intake/exhaust) & valve seat inserts
- Springs, retainers, keepers/locks
- Guide driver + reamer/hone (machine to spec after install)
What’s In The Box
- (1) Genuine Cummins Valve Stem Guide (3904409)
- Head kit components sold separately.
Install Tips
- Confirm cylinder head P/N; many 12V heads use this as the exhaust guide.
- Heat head / chill guides; press in with proper driver. Always finish with ream/hone to valve stem spec.
- Set installed height/protrusion per service manual; check valve-to-guide clearance and concentricity.
FAQ
WILL THIS FIT MY 1989–1998 5.9L 12-VALVE?Yes—this guide is widely used on 12-valve B-Series cylinder heads found in 1989–1998 Ram 2500/3500. Verify by ESN and head casting/BOM before ordering.
IS 3904409 FOR INTAKE OR EXHAUST?It’s commonly an exhaust valve stem guide on 2-valve B-Series heads. Some heads use different P/Ns intake vs. exhaust—check your head’s parts list.
HOW MANY DO I NEED?12-valve heads have 12 guides total. Typical 3904409 usage is 6 exhaust guides; intake may be a different number. Confirm your head’s BOM.
DOES THIS REQUIRE MACHINING?Yes. Proper installation requires pressing the guide and then reaming/honing to spec. Always verify valve-to-guide clearance per the service manual.
IS THIS A GENUINE CUMMINS PART?Yes—this listing is for OE Cummins 3904409. Cross-references like PAI 192040 or Interstate-McBee M-3904409 are aftermarket identifiers.
