Cummins 3931623 — Genuine Valve Tappet (Lifter) for 5.9L 6BT & 3.9L 4BT

MPN: 3931623  |  Also Known As: valve lifter, cam follower, tappet  |  Supersedes / Cross-Refs (ID): 3901787, 3907240, 3925031

Genuine Cummins flat tappet engineered for the B-Series mechanical-injection era. Direct-fit on 5.9L 6BT (12-valve) and 3.9L 4BT platforms. Sold individually; order the correct quantity for your engine (12 for 6BT, 8 for 4BT).

Features & Benefits

• OE geometry & hardening to protect cam lobes and ensure quiet operation.
• Direct-fit replacement for 1989–1998 5.9L 12-valve (VE & P7100) and common 4BT builds.
• Durable, consistent metallurgy for long service life on stock and work applications.
• Ideal when installing a new cam or refreshing a high-mileage valvetrain.
• Backed by Cummins quality for fit, function, and reliability.

Verified Fitment (Automotive)

Industrial/Off-Highway: 3.9L 4BT, 5.9L 6BT, and seen on some 8.3L C-Series/ISC/QSC builds—verify by ESN prior to ordering.

Specifications

• Type: Mechanical flat tappet (valve lifter), cam follower
• OE Part Number: 3931623
• Supersedes / Cross-Refs (ID): 3901787, 3907240, 3925031
• Quantity Required: 12 per 6BT engine; 8 per 4BT engine (sold individually)

Often Paired With

• Camshaft (OE or performance) — replace tappets any time a new cam is installed
• Pushrods & rockers — inspect/replace if bent or worn
• Tappet cover gasket / grommets — replace seals during service

What’s In The Box

• (1) Genuine Cummins Valve Tappet (3931623)

Installation Tips

• Inspect cam lobes for wear; do not reuse worn tappets on a new cam.
• Pre-lube tappet faces and cam lobes; follow Cummins torque & lash procedures.
• Set valve lash to factory spec after assembly and re-check after initial heat cycle.

FAQ

WILL THIS FIT MY 1989–1998 12-VALVE RAM?

Yes—direct-fit for 5.9L 12V (VE ’89–’93 and P7100 ’94–’98) Ram 2500/3500 applications.

HOW MANY DO I NEED?

Order 12 for a complete 6BT engine, or 8 for a 4BT engine. Sold individually.

DOES THIS FIT 24-VALVE OR COMMON-RAIL ENGINES?

No—1998.5–2002 24V (VP44) and 2003+ common-rail engines use different tappets. Check your VIN/ESN for the correct part number.

IS THIS A GENUINE CUMMINS PART?

Yes—OE Cummins 3931623 with factory geometry and surface hardening.

WHAT ARE THE COMMON CROSS-REFERENCES?

Common legacy identifiers include 3901787, 3907240, and 3925031. Use ESN to confirm interchange.