General. The General Motors 8-268 or 8-268A engine is used on board modern submarines as an auxiliary engine. | 12 AUXILIARY ENGINES A. GENERAL MOTORS 8-268 AND 8-268A ENGINES 12A1. General. The General Motors 8268 or 8-268A engine is used on board modern submarines as an auxiliary engine. It is located in the lower flats of the after engine rooms and may be used for directly charging the batteries or carrying the auxiliary load and indirectly for ship propulsion. The GM 8-268 is an 8-cylinder in-line 2-cycle air started engine rated at 300 kw generator output at 1200 rpm. In general the individual parts of the engine are similar to but smaller than the corresponding parts in the GM 16-278A. For example the camshafts exhaust valve and rocker lever assemblies injectors pistons cylinders liners and connecting rods are almost miniature replicas of the 16-278A parts. The main differences between the engines appear in the construction and design of the various systems such as the scavenging air exhaust lubricating oil and fuel oil systems as well as in the fact that the 8-268 is an in-line engine. 12A2. Engine stationary and moving parts. a. Cylinder block. The cylinder block is the main structural part of the engine. It is composed of forgings and steel plates welded together combining strength with light weight. The upper and lower decks of the cylinder block are bored to receive the cylinder liners. The space between the decks is the scavenging air chamber. The bore in the lower deck is constructed with a groove which serves as a cooling water inlet for the liner. The cylinder liners are located in the cylinder block by means of dowel pins in the upper deck. The camshaft bearing lower support is an integral part of the cylinder block located at the extreme top of the block. The bearing cape and bearing supports are match-marked and must be kept access to the crankcase. Eight are located on one side and seven on the other. The remaining handhole is covered by the air maze which may be moved. Seven of the covers are of the safety type each having four spring-loaded plates which
