Product Description
CUMMINS 3957912 OEM VALVE STEM SEAL (TOP HAT STYLE) – 5.9L 12V 6BT (1989–1998)
The CUMMINS 3957912 OEM valve stem seal is the later “top hat” style seal used on many 5.9L 12-valve 6BT cylinder heads. It controls oil at the valve stem so your 12V doesn’t burn oil, foul plugs, or haze at idle. This genuine Cummins part drops into properly machined B-series heads and is a perfect match for 1989–1998 Dodge Ram 2500/3500 5.9L 12V Cummins as well as a long list of 4BT/6BT industrial and off-highway engines (always confirm by ESN).
Whether you’re freshening up a work truck, building a tow rig, or doing a full Cummins 5.9L 12V top-end rebuild, using real Cummins 3957912 seals helps stabilize idle quality, reduce oil consumption, and keep your combustion chambers clean. Order twelve (12) seals per engine when the head is configured for top-hat style seals.
Key Features
- Genuine Cummins 3957912 “top hat” valve stem seal.
- Controls oil at the valve stem to cut down on oil burning and smoke.
- Designed for B-series heads updated or machined for top-hat style seals.
- Compatible with many 4BT/6BT/ISB/QSB industrial and on-highway engines (verify by ESN).
- Sold individually – 12 seals required for a complete 12-valve engine.
Fitment
Automotive – Dodge Ram
- 1989–1993 Dodge D/W 250 & 350 – 5.9L 12V Cummins (6BT)
- 1994–1998 Dodge Ram 2500 & 3500 – 5.9L 12V Cummins (6BT)
Common B-Series / Industrial / Off-Highway (verify by ESN)
- 4B3.9, 6B5.9, B5.9, B5.9G, B6.7S
- G5.9, G8.3, ISB/ISBe 5.9/6.7
- QSB3.9, QSB4.5, QSB5.9, QSB6.7
- QSC8.3, QSL9 and other B-series variants where 3957912 is specified
Always confirm by engine serial number (ESN) and cylinder head part number when working on industrial/off-highway engines.
When to Use 3957912 vs. 3921640
Many early 12-valve heads used the original non–top-hat seal CUMMINS 3921640 OEM VALVE STEM SEAL . Later and updated heads (or machined heads) often run the top-hat style 3957912. If your retainers/rotators and guides are already set up for a top-hat seal, 3957912 is usually correct.
Cross-Reference & Related Cummins Parts (CPP Links)
- Early-style valve stem seal: CUMMINS 3921640 OEM VALVE STEM SEAL – RAM 5.9L 12-VALVE (1989–1998)
- Intake valve stem guide: CUMMINS 3904408 OEM VALVE STEM GUIDE (INTAKE, 60.50MM) – 5.9L 12V
- Exhaust valve stem guide: CUMMINS 3904409 OEM VALVE STEM GUIDE (51.75MM) – 5.9L 12-VALVE (1989–1998)
- Intake valve spring: CUMMINS 3926700 OEM VALVE SPRING – 5.9L 12V / 4BT & 6BT B-SERIES
- Valve cover gasket: CUMMINS 3930906 OEM VALVE COVER GASKET – 5.9L 12V (1989–1998) | 4BT/6BT B-SERIES
- Valve cover with oil fill: CUMMINS 3928405 OEM VALVE COVER WITH OIL FILL – 4BT/6BT 5.9L (1989–1998 12V)
What’s Included
- (1) Genuine Cummins 3957912 valve stem seal – top hat style
Note: Order quantity 12 to service one complete 12-valve engine.
Installation Notes
- Use proper valve spring compressor tools and protect valve stems during disassembly.
- Lightly lubricate the seal lip and press the seal squarely onto the guide until fully seated.
- If you are converting from the original early-style seal to 3957912, confirm retainer/rotator and guide compatibility or follow your machine shop’s recommendations.
- Always verify valve-to-guide clearance and installed height per Cummins specs.
Specifications for cummins 3957912
| Field | Value |
|---|---|
| Part Number | 3957912 |
| Brand | Cummins (Genuine OEM) |
| Description | Valve stem seal – top hat style (intake/exhaust) |
| Engine Platform | 5.9L 12V Cummins 6BT, plus 4BT/6BT/ISB/QSB B-series applications where 3957912 is specified |
| Automotive Fitment | 1989–1998 Dodge D/W & Ram 2500/3500 with 5.9L 12-valve Cummins (6BT) |
| Qty Required (12V head) | 12 per engine (sold individually) |
| UPC | 622329276852 |
| GTIN | 622329276852 |
| Shipping Weight | Approx. 0.03 lb each (single seal) |
| Shipping Info | Ships as a small, lightweight part – typically in a padded mailer or small box |
| Cross Reference (kits) | Commonly included in Cummins kits such as 2868075, 2868076, 2881955, 3356970, 3356971, 3356972, 3356973, 3356977, 3357301, 3357304, 3358002, 3358220 (verify by ESN) |
| E-Codes / Emissions | Used on many Euro 2 and global 5.9L B/ISB applications; confirm by ESN and emissions label |
| Prop 65 | Not specifically listed for Prop 65; standard handling and shop safety recommended |
FAQ
WILL THIS FIT MY 1989–1998 5.9L 12-VALVE?In most cases, yes. Cummins 3957912 is the OEM top-hat style valve stem seal used on many 5.9L 12-valve B-series heads. You must confirm that your cylinder head is set up for top-hat style seals (retainers/rotators and guides) before ordering.
HOW MANY SEALS DO I NEED FOR A COMPLETE ENGINE?
A 12-valve 5.9L Cummins uses 12 valve stem seals total – one per valve. If your head is configured for 3957912 on all valves, order quantity 12 to service the entire engine.
IS THIS THE SAME AS THE ORIGINAL 3921640 SEAL?
No. CUMMINS 3921640 is the older non–top-hat style seal. 3957912 is the later top-hat design. Some heads can be updated from 3921640 to 3957912 with the correct guides and retainers; others should keep the original style. Always verify your hardware and machine shop recommendations.
DO THESE SEALS WORK ON BOTH INTAKE AND EXHAUST VALVES?
When the cylinder head is machined and set up for top-hat style seals, 3957912 is commonly used on both intake and exhaust positions. Always check your head’s bill of materials (BOM) and follow Cummins service information for your ESN.
DO I NEED MACHINE WORK TO USE 3957912?
If your head is already configured for top-hat seals, 3957912 is usually a direct fit. If you are converting from the early seal design, machining and updated retainers/rotators and guides may be required. Coordinate with a qualified machine shop for proper setup.
IS THIS A GENUINE CUMMINS PART?
Yes. This listing is for an OEM Cummins 3957912 valve stem seal sourced through CPP Diesel. We also offer high-quality aftermarket options on separate product pages when you need a budget-friendly alternative.
