Cummins 3927948 — Genuine 12mm Main Bearing Cap Bolt for 5.9L/6.7L

MPN: 3927948  |  Also Known As: main cap bolt, main bearing bolt, fracture-resistant screw  |  Thread/Size: M12 x 1.50 x 119 mm

Genuine Cummins main bearing cap bolt engineered to clamp the crankshaft main caps with OE strength and consistency. Ideal for stock rebuilds and performance refreshes. Sold individually; 14 required per 5.9L/6.7L engine (10 for 4BT).

Features & Benefits

• OE metallurgy and finish for reliable clamping under heat and load.
• Precision thread and under-head geometry for accurate torque/angle.
• Direct-fit replacement for ISB 5.9L and 6.7L main cap fasteners.
• Service-bay friendly: replace during any bottom-end rebuild to avoid mixed hardware.

Verified Fitment (Automotive)

Industrial/Off-Highway: 4BT/6BT/ISB/QSB applications that use 12 mm main bolts — verify by ESN before ordering.

Specifications

• Type: Main bearing cap bolt (engine bottom-end fastener)
• OE Part Number: 3927948
• Size: M12 x 1.50 x 119 mm
• Quantity Required: 14 per 5.9L/6.7L; 10 per 4BT (sold individually)

Often Paired With

• Main bearing set (OE or performance)
• Rear main seal kit (year/engine specific)
• Assembly lube for bearings and fasteners

What’s In The Box

• (1) Genuine Cummins Main Bearing Cap Bolt (3927948)

Installation Tips

• Clean threads in block and under-head seating surfaces; chase if necessary.
• Lightly oil threads and under-head if specified by service manual; torque/angle to spec in sequence.
• Replace as a set during rebuilds; do not reuse damaged or stretched fasteners.

FAQ

HOW MANY MAIN CAP BOLTS DO I NEED?

For 5.9L/6.7L inline-6 engines you need 14 bolts total; for 4BT inline-4 you need 10 bolts. This item is sold individually.

WILL THIS FIT MY 5.9L OR 6.7L RAM?

Yes—3927948 covers 5.9L (1998.5–2007) and 6.7L (2007.5–2018) ISB applications. Verify by VIN/ESN for absolute accuracy.

ARE THESE REUSABLE?

Best practice is to replace main cap bolts during a rebuild. Always inspect for stretch or damage and follow Cummins’ service guidance.

WHAT IS THE SIZE/SPEC?

M12 x 1.50 thread, 119 mm length. Use the factory torque/angle procedure from the Cummins manual.

IS THIS A GENUINE CUMMINS PART?

Yes—OE Cummins part 3927948 with OEM fit and clamping performance.