PLUG-ORIFICE 8E6051 - Caterpillar

3508B (2BM, 7SM),
3512B (7HM, 4TN),
3516B (8CN, 8KN) Marine;
3508B (3DM),
3512B (8EM),
3516B (9AN) Marine Auxiliary;
3508B (4GM, 6PN),
3512B (8RM, 6WN),
3516B (6HN, 7RN) High Speed Generator Set;
3508B (5PS),
3512B (3ZW) Locomotive EnginesDescription of Change: A new basic cylinder head group is used in the basic engine arrangements in these high speed commercial engines. The new cylinder head group includes 20 degree inlet valves and 45 degree exhaust valves. The 45 degree exhaust valve provides a wider seating surface, which increases heat transfer and reduces contact stress. The increased angle also provides more aggressive seat scrubbing, which reduces combustion product buildup on the seating surface.Adaptable To: The new 145-3216 Basic Cylinder Head Group replaces the former 155-5273 Basic Cylinder Head Group in the 101-0830 Cylinder Head Group on these 3500B high speed commercial engines. The new 145-3216 Basic Cylinder Head Group is effective with the engines listed in the chart. The new basic cylinder head group should be used for top end overhauls or major overhauls. The new basic cylinder head group may be used individually in repair of a valve failure. The former basic cylinder head groups may also be rebuilt using the following components: * 133-9306 Precision Valve Guides* 137-6856 Seals* 130-2607 Premachined Valve Seat Inserts (Inlet)* 121-2028 Inlet Valves* 130-2608 Premachined Valve Seat Inserts (Exhaust)* 121-9835 Exhaust Valves.
DO NOT perform any machining or lapping on the valves or seat inserts after installation. The bench vacuum test SHOULD NOT be used. Proper seating is established very early in the break-in period. It is also VERY IMPORTANT to follow up with Bridge and Valve Adjustments at the first 250 hours or the next oil change, NOT to exceed 500 hours.