New Stronger Cylinder Head Bolts Used

Description of Change: New cylinder head bolts are used in these commercial engines. The new stronger bolts meet or exceed SAE Grade 8 tensile strength and proof load tests. The 3/4- 16 UNF threads are rolled into the bolts after heat treat. The new bolts can be identified by the standard “Grade 8” bolt head marking of six equally spaced marks radiating outward on the top of the 12 point bolt head. See the illustration.

Identification “Marks” on top of bolt heads on the new 124-1855 Cylinder Head Bolt.

Adaptable To: The new 124-1855 Bolt [3/4- 16 UNF thread, 194.0 mm (7.64 in) long] replaces the former 9X-8904 Bolt. Twenty 124-1855 Bolts are used on each cylinder head. The 6 rocker arm bracket bolts remain unchanged. The new cylinder head bolts are effective with:

*3406C (90U19998, 6TB15397) Industrial
*3406C (4TB5051) Marine
*3406C (2WB16660, 4RG2510, 4JK196) Generator Set
*G3406C (4FD1042, 1RK61) Engines
The new cylinder head bolts are adaptable to all earlier 3406 Engines.

Publication Date -09/05/1996

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