Head Bolt 3.9 4B/4BT 5.9 6B/6BT Cummins

New Cylinder Head Bolt 3.9 4B/4BT 5.9 6B/6BT Cummins Engines.

This is a 12mm Hexagon Flange Bolt M12 x 1.75 x 70mm or 12 mm x 70 mm.

Also fits some QSB4.5 engines.

This is the shortest of the 3 sized head bolt. The 4BT engine takes 4 of these bolts and the 6BT takes 6 of them.

Scroll down for more detailed compatibility information.

Part Number: 3903938 3920779

Weight: 0.5 lbs.

Price: $3.00

Short Product Description:

3903938 Cylinder Head Bolt

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Questions and Answers:

Q: Which bolts do I need for a complete cylinder head bolt set for the 4B 8v and 6B 12v engines?	11/18/2024
A: If you have a 4B engine, then you need 4 of 3920781, 4 of 3920779 and 10 of 3920780. If you have a 6B engine, then you need 6 of 3920781, 6 of 3920779 and 14 of 3920780.
Q: How should I torque the head bolts on 4BT 8v and 6BT 12v cylinder heads?	1/29/2025
A: According to the Haynes Repair Manual the cylinder head bolts should first be torqued from the inside bolts and then outside bolts to 66 ft-lbs. Then the longer rocker arm head bolts should be torqued to 89 ft-lbs. Last all the cylinder head bolts should be turned an additional 90 degrees. This is always done from the inside bolts, and then the outer bolts.

Description: 3903938 Cylinder Head Bolt

Price: $3.00