2003/02/01 Caterpillar

Engine:

G3412 (S/N: 7DB1784-UP; CTP259-UP)

G3412C (S/N: 6ZM500-UP; 8LW227-UP)

Description of Change: The following changes have been made in order to improve the overall reliability of the G3412 Engine. A new taller cylinder head group is now in production on G3412 Engines. The new cylinder head is 13 mm (0.51 inch) taller than the former cylinder head. The new cylinder head improves cooling of the exhaust valve guides. The cooler exhaust valve guides increase the heat dissipation from the exhaust valves. The new cylinder head has longer valve guides. The longer valve guides provide increased support for the valves. The new cylinder head has reduced overhang of the exhaust valve in the exhaust port. The reduced overhang improves the rigidity of the valve. The improved rigidity of the valve improves the ability to guide the valve as the valve is seated. The internal cooling passages of the cylinder head have been modified in order to improve the overall cooling of the components of the cylinder head.

Adaptable To: The increased height of the new cylinder head requires new valve guides and new valves. Refer to the table below for the new valve guides and new valves.

Table 1

Intake	Exhaust
213-7536 Valve Guide	213-7537 Valve Guide
212-0932 Inlet Valve	212-0933 Exhaust Valve

New hardware will be required to install the new cylinder head groups. The hardware that is required is based on the ignition system of the individual engine. Conversion kits have been released in order to facilitate conversion from the original cylinder head to the new taller cylinder head. Refer to the table below for a list of the required hardware.

Table 2

Ignition System	Electronic Ignition System (EIS)		Electronic Ignition System (EIS) / Canadian Standard Association (CSA)		Magneto or Caterpillar Digital Ignition System (CDIS) / Canadian Standard Association (CSA)
	Pt. No.	Pt. No.	Pt. No.	Pt. No.	Pt. No.	Pt. No.
	New	Replaces	New	Replaces	New	Replaces
Cylinder Head Gp	206-7745	200-0607	206-7745	200-0607	206-7745	200-0606
Rebuilt Cylinder Head Group	10R-1134	0R-9486	10R-1134	0R-9486	10R-1134	0R-9485
Conversion Kit (1)	226-1797	N/A	226-1798	N/A	226-1796	N/A

( 1 )

Use this conversion kit in order to convert from a short cylinder head to a tall cylinder head.

Table 3

Cylinder Head Gasket Kit (1)	Single		Multiple
	New	Replaces	New	Replaces
	226-9418	8T-3370	226-9417	8T-3369

( 1 )

Use this cylinder head gasket kit in order to replace a tall cylinder head with a tall cylinder head.

A lower torque is used for the cylinder head bolts in order to prevent distortion of the cylinder head bottom deck. The Special Instruction, REHS1362 has been released in order to explain the torque procedure for the new cylinder head group.