- Engine:
- G3406 (S/N: 4FD1-UP; 1RK1-UP; CTS1-UP)
Description of Change: A new taller cylinder head group is now in production on G3406 Engines. The new cylinder head is 12 mm (0.472 inch) taller than the former cylinder head. The new cylinder head improves the engines' overall reliability. 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 Table 1 for the new valve guides and new valves.
| Intake | Exhaust |
| 212-0932 Inlet Valve | 212-0933 Exhaust Valve |
| 224-1300 Valve Guide | |
| Cylinder Head Group | |
| Old Part | New Part |
| 200-0615 Cylinder Head Gp | 223-6519 Cylinder Head Gp |
| 0R-7316 Cylinder Head Gp | 10R-1970 Cylinder Head Gp |
| Required Parts | |
| Quantity | Part |
| 1 | 226-1803 Conversion Kit (1) |
| 2 | 0S-1591 Bolts |
| 2 | 9M-4136 Spacers |
| ( 1 ) | Use this conversion kit in order to convert from a short cylinder head to a tall cylinder head. |
| Cylinder Head Gasket Kit (1) | |
| Old Part | New Part |
| 7X-7657 Gasket Kit | 234-8829 Gasket Kit |
| ( 1 ) | Use this cylinder head gasket kit in order to replace a tall cylinder head with a tall cylinder head. |
 | |
| Illustration 1 | g01083215 |
Top view of the front housing fastener group (1) Cylinder head (2) Plate (3) Bolts (4) Front housing (6) Lifting eye | |
Additional hardware is required in order to adapt the 4N-6006 Front Housing Fastener Gp for the taller cylinder head. Longer bolts and spacers are needed in order to retrofit the fastener group. Spacers are placed under the portion of plate (2) that extends over front housing (4). Longer bolts (3) are installed through the plate, and the spacers. The longer bolts are threaded into the front housing. Refer to Table 3 and refer to Figure 1.
A lower torque is used for the cylinder head bolts in order to reduce distortion of the cylinder head bottom deck. The Special Instruction, REHS1433 will explain the torque procedure for the new cylinder head group. This Special Instruction is included in the conversion kit.
The cylinder head is effective with the engines that are listed in Table 5.
| Engine Serial Number |
| S/N:1RK110 and Up |
| S/N:4FD2648 and Up |
| S/N:CTS382 and Up |