Product Description
Cummins 3921640 — Valve Stem Seal (Intake & Exhaust)
MPN: 3921640 | Also Known As: valve stem oil seal | Cross-Refs (ID only): 3901097, 3921639
Genuine Cummins valve stem seal for 5.9L 12-valve applications. Restores proper oil control at the valve guide to reduce oil consumption and exhaust smoke. Sold individually; 12 required per engine. :contentReference[oaicite:0]{index=0}
Why This Part
- ✓ OE sealing geometry for long service life and clean combustion.
- ✓ Direct-fit replacement for 1989–1998 Ram 5.9L 12-valve (verify by VIN/ESN).
- ✓ Helps cut oil consumption and startup smoke from worn seals.
- ✓ Works on both intake and exhaust valves (12 total per engine). :contentReference[oaicite:1]{index=1}
Quick Specs
| Type | Valve stem oil seal (intake & exhaust) |
|---|---|
| OE Part # | 3921640 |
| Qty Required | 12 per engine (sold individually) |
| Cross-References | 3901097, 3921639 (for identification) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1998 | 5.9L 12-Valve (6BT) | D/W 250–350 (’89–’93), Ram 2500/3500 (’94–’98) |
Industrial/Off-Highway: Used on many B-Series applications (4B/6B/ISB/QSB). Always confirm by ESN. :contentReference[oaicite:2]{index=2}
Often Paired With
- Valve Spring Compressor (12V): XDP XD312
- Valve Spring Keepers: Cummins 3900250
- Valve Cover Gasket: Cummins 3930906
Popular combos taken from XDP’s “Frequently Bought Together.” :contentReference[oaicite:3]{index=3}
What’s In The Box
- (1) Genuine Cummins Valve Stem Seal (3921640)
- Tools/gaskets sold separately (see “Often Paired With”).
Install Tips
- Replace all seals during valve service; inspect guides for wear.
- Use the proper installer; do not nick the sealing lip.
- Torque rockers to spec; verify lash after reassembly.
FAQ
WILL THIS FIT MY 1989–1998 5.9L 12-VALVE CUMMINS?Yes—this is the OE valve stem seal used on 1989–1998 Dodge/Ram 5.9L 12-valve engines. Verify by VIN/ESN if components have been changed. :contentReference[oaicite:4]{index=4}
HOW MANY SEALS DO I NEED?There are 12 valves on the 12-valve engine—order 12 seals for a complete set. :contentReference[oaicite:5]{index=5}
ARE THESE FOR INTAKE AND EXHAUST?Yes—3921640 is used on both intake and exhaust valves. :contentReference[oaicite:6]{index=6}
WHAT ARE COMMON CROSS-REFERENCE NUMBERS?Common identifiers include 3901097 and 3921639 (for cataloging/ID only). :contentReference[oaicite:7]{index=7}
DO THESE FIT OTHER CUMMINS B-SERIES ENGINES?Yes—this seal appears across many 4B/6B/ISB/QSB applications in industrial/off-highway use. Always verify by ESN. :contentReference[oaicite:8]{index=8}
