- Engines:
- G3606 (S/N: 3XF)
- G3608 (S/N: 4WF)
- G3612 (S/N: 1YG)
- G3616 (S/N: 4CG)
Reference: Engine News, SEBD9281, January 2000, "New Basic Cylinder Head Groups Include Premachined Valve Seat Inserts For Improved Reliability"
Description of Change: New cylinder head groups are used on these engines. The new cylinder head groups provide the following changes:
- Improved cooling of the exhaust valve guide
- Improved serviceability of the valve seats
- Improved wear characteristics for applications with a High Compression Ratio (10.5:1 and 11:1) and applications with a Low BTU (Bio-gas and landfill)
Except for the exhaust valves, the new cylinder head groups for applications with a High Compression Ratio and applications with a Low BTU are nearly identical to the cylinder head groups for applications with a Low Compression Ratio. Also, the applications with Low BTU are the only configuration that will use the 153-7002 Valve Stem Seal (Exhaust).
Adaptable To: The table identifies the new cylinder head groups. The table also identifies the components of the new cylinder head groups. The new cylinder head groups are adaptable to all of the above engines.
| Cylinder Head Groups | |||
|---|---|---|---|
| Natural Gas Low Compression Ratio (9:1) Part Number |
Natural Gas High Compression Ratio (10.5:1 and 11:1) Part Number |
Low BTU Fuel (1) Low Compression Ratio (9:1) Part Number |
|
| Cylinder Head Group (2) | 7C-0400 | N/A | 172-2227 |
| Basic Cylinder Head Group | 171-3994 | 194-3250 | 185-3606 |
| Exhaust Valve Seat Insert prefinished 20 Degree |
171-3993 | ||
| Inlet Valve Seat Insert prefinished 20 Degree |
171-3992 | ||
| Insert (Prechamber assembly) Standard Size |
148-7142 | ||
| Insert (Prechamber assembly) 0.25 mm Oversize |
148-7143 | ||
| Insert (Prechamber assembly) 0.50 mm Oversize |
148-7144 | ||
| Exhaust Valve 20 Degree |
154-2417 | 185-1103 | |
| Inlet Valve 20 Degree |
4P-2854 | ||
| Valve Stem Seal | N/A | N/A | 153-7002 |
| Rotator Assembly | 189-4583 | ||
| Inlet and Exhaust Valve Guide Standard size |
175-6344 | ||
| Inlet and Exhaust Valve Guide 0.5 mm Oversize |
183-5074 | ||
| Inlet and Exhaust Valve Guide 1.0 mm Oversize |
183-5073 | ||
| ( 1 ) | This includes applications that use landfill gas or Bio-gas. |
| ( 2 ) | These cylinder head groups are not available for parts service at this level. |
Serviceability
Except for the valve seat inserts, the new cylinder heads can be serviced and rebuilt with the existing guidelines. The new 171-3992 Valve Seat Insert (Inlet) and the new 171-3993 Valve Seat Insert (Exhaust) can be installed without any special operations for finishing the valve seat in the new cylinder heads. These valve seat inserts are premachined to the proper specifications for the valve face angle. The machining process has been improved for the following parts: the cylinder head, the valve seat inserts and valve guides. This allows these components to be assembled together without any further machining.
The new cylinder head groups will meet the service intervals that are identified in the guidelines for maintenance.
Note: The 171-3992 Valve Seat Insert (Inlet) and the new 171-3993 Valve Seat Insert (Exhaust) can not be used with the earlier cylinder head casting.
The 187-6273 Prechamber Machining Tool Group can be used if the seat in the cylinder head for the prechamber assembly requires attention. Refer to Tool and Operating Manual, NEHS0790, "Using The 187-6273 Prechamber Machining Tool Group".