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

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

This is a 12mm Hexagon Flange Screw M12 x 1.75 x 180mm or 12 mm x 180 mm.

Also fits some QSB4.5 engines.

This is actually a cylinder head bolt that also holds the rocker arm down.

This is the longest of the head bolts. The 4BT engine uses 4 and the 6BT uses 6 of these bolts.

Scroll down for more detailed compatibility information.

Part Number: 3920781 3903940 3902344 040050

Weight: 0.5 lbs.

Price: $3.00

Short Product Description:

3920781 Rocker Arm Bolt

Quantity to Add:

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Questions and Answers:

Q: Do you have to replace Cummins head bolts every time?	8/8/2024
A: No, Cummins has an allowable stretch spec. As long as you are within that, you can reuse the old bolt. Some people choose to always replace them, though.
Q: What is the torque spec for the cylinder head bolts on a Cummins 4BT 8v or 6BT 12v engine?	9/30/2024
A: According to the Haynes Repair Manual the cylinder head bolts should first be torqued in order to 66 ft-lbs. The order is from the inside out. Then the long rocker arm bolts should be torqued to 89 ft-lbs. Finally all the cylinder head bolts should be turned an additional 90 degrees. Again, this is done in order, meaning from the inside out.
Q: How many of these bolts are on the 4B and 6B engines?	11/18/2024
A: If you have a 4B engine, then there are 4 of these long bolts. If you have a 6B engine, then you have 6 of these bolts on your engine.
Q: What is 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.

3920781 Screw, Hex Flange Head Cap Quantity: 6 Remarks: Ref No : 11 3904679 Engine Year: 1988 BT5.9 160 CPL:804 Sample ESN: 44243058

3920781 Screw, Hex Flange Head Cap Quantity: 6 Remarks: Ref No : 11 3923262 Engine Year: 1996 B5.9 (215) CPL:2175 Sample ESN: 56326974

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3904679 Engine Year: 1988 4BT3.9 (105) CPL:858 Sample ESN: 44258612

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3904679 Engine Year: 1988 4B3.9 CPL:591 Sample ESN: 21021339

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3904679 Engine Year: 1995 4BT3.9-C CPL:730 Sample ESN: 21021339

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3923262 Engine Year: 1997 4B3.9 CPL:767 Sample ESN: 21021339

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3284377 Engine Year: 2006 S4D102LE-2 CPL:1493 Sample ESN: 46659758

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3284377 Engine Year: 2000 B3.9 130 CPL:1839 Sample ESN: 46114812

3920781 Screw, Hex Flange Head Cap Quantity: 4 Remarks: Ref No : 11 3284377 Engine Year: 2006 QSB4.5 CPL:8401 Sample ESN: 46114812

3920781 Screw, Hex Flange Head Cap Quantity: 6 Remarks: Ref No : 11 3923262 Engine Year: 1997 B5.9 (190) CPL:1551 Sample ESN: 46114812

3920781 Screw, Hex Flange Head Cap Quantity: 6 Remarks: Ref No : 11 3923262 Engine Year: 1996 B5.9-C177 CPL:599 Sample ESN: 46114812

3920781 Screw, Hex Flange Head Cap Quantity: 6 Remarks: Ref No : 11 3284377 Engine Year: 1999 BT5.9-C160 CPL:1288 Sample ESN: 46114812

Description: 3920781 Rocker Arm Bolt

Price: $3.00