3512B Marine Auxiliary Engine Caterpillar

The engine block is a vee block configuration. The engine cylinders are arranged into two banks of six cylinders. The cylinders are oriented at an angle of 60 degrees with respect to each other. The front gear housing and the rear gear housing are constructed of cast iron. The front gear housing and the rear gear housing are mounted directly to the sub-base. The main bearing caps are fastened to the cylinder block with four bolts in each cap.

The cylinder liners are constructed of cast iron. The cylinder liners can be removed for replacement. The top surface of the cylinder block is the seat for the cylinder liner flange. Engine coolant flows around the cylinder liners in order to keep the cylinder liners cool. Three O-ring seals around the bottom of the cylinder liner make a seal between the cylinder liner and the cylinder block. A filler band goes under the cylinder liner flange. This makes a seal between the top of the cylinder liner and the cylinder block.

The engine has a separate cylinder head for each cylinder. Two inlet valves and two exhaust valves, which are controlled by a pushrod valve system, are used for each cylinder. Valve guides without shoulders are pressed into the cylinder heads. The opening for the unit injector is located between the four valves. A third lobe on the camshaft moves the pushrod that operates the unit injector. Fuel is injected directly into the cylinder. Refer to this Systems Operation, "Valve System Components" for further information.

There is an aluminum spacer plate between each cylinder head and the cylinder block. Coolant goes out of the cylinder block through the spacer plate and into the cylinder head through eight openings in each cylinder head face. Water seals are used in each opening to prevent coolant leakage. Gaskets seal the engine oil drain line between the cylinder head, the spacer plate, and the cylinder block.

Illustration 1	g00926828
(1) Camshaft cover with an oil filler (2) Camshaft cover (3) Crankcase cover

There are twelve camshaft covers that are located on the engine. There are twelve crankcase covers that are located on the engine. Removable side covers are installed on each side of the engine block in order to facilitate the inspection and maintenance of the engine. The connection for the engine oil filler is incorporated into the number seven camshaft cover. Camshaft covers (1) allow access to the camshaft and valve lifters. Crankcase covers (2) allow access to the crankshaft connecting rods, main bearings, and piston cooling jets. When the covers are removed, all the openings can be used for inspection and service.