6643677 Volvo.Penta Bolt

Cylinder Head Assembly
The cylinder heads are a one-piece cast iron head. The cylinder head supports the camshaft. Steel reinforced camshaft bearings are pressed into each bore for the camshaft. The bearings are lubricated under pressure. The cylinder head contains two inlet valves and two exhaust valves for each cylinder, which are controlled by the rotation of the camshaft. Bridge dowels have been eliminated as the valve train uses floating valve bridges.The unit injector is mounted in a stainless steel adapter. This adapter has been pressed into the cylinder head injector bore. Pistons, Rings And Connecting Rods
The piston is a one-piece design that consists of a forged steel crown and a skirt. The piston is retained by the piston pin to the small end of the connecting rod. The pistons have three rings that are located in grooves in the steel crown. These rings seal the combustion gas. The rings provide control of the oil. The top ring has a barrel face. This ring is a Keystone ring with a plasma face coating. The second ring has a tapered face and the ring has a coating of chrome finish for the face. The third ring is the oil ring. The third ring has a coil spring expander. There are four holes that are drilled from the piston oil ring groove to the interior of the piston. These holes return excess oil from the oil ring groove to the crankcase.The connecting rod is a conventional design. The cap of the connecting rod is attached to the shank by four bolts that are threaded into the shank. Each side of the small end of the connecting rod is machined at an angle of 12 degrees in order to fit within the piston cavity.Crankshaft
The crankshaft converts the combustion force in the cylinder into rotating torque. A vibration damper is used at the front of the crankshaft in order to reduce the torsional vibrations.The crankshaft drives a group of gears on the front and the rear of the engine. These gear trains provide power for the following components: camshaft, water pump, oil pump, fuel transfer pump and accessory items that are specific to the application.The cylinder block has seven main bearings that support the crankshaft. The cylinder block uses four bolts to hold each of the bearing caps into the block. Pressurized oil is supplied to all bearing surfaces through drilled holes in the webs of the cylinder block. The oil then flows through drilled holes in the crankshaft in order to provide oil to the connecting rod bearings.Seals and wear sleeves are used at both ends of the crankshaft. The seals and wear sleeves are used for easy replacement and reduction of maintenance cost.Camshaft
The camshaft has three lobes at each cylinder. These lobes allow the camshaft to operate the unit injector, the exhaust valves, and the inlet valves. The camshaft is supported in the cylinder head by seven journals which are fit with bearings. The camshaft gear contains integral roller dampers that counteract the torsional vibrations that are generated by the high fuel pressure during fuel injector operation. The design reduces gear train noise. The camshaft is driven by a fixed idler gear which is turned by another fixed idler gear which is turned by a cluster idler gear in the gear train. Each bearing journal is lubricated from the oil manifold in the cylinder head. A thrust plate that is located at the front controls the end play of the camshaft. Timing of the camshaft is accomplished by aligning marks on the crankshaft gear and idler gear, and camshaft gear with a mark on the front timing plate.Vibration Damper
The twisting of the crankshaft is called torsional vibration. The torsional vibration is caused by the regular power impacts along the length of the crankshaft. The vibration damper is installed on the front end of the crankshaft. This vibration damper is used to reduce the torsional vibrations. This eliminates any damage that could occur to the crankshaft.The rubber damper is made of an outer hub connected to an inner hub by a rubber ring. The rubber makes a flexible coupling between the outer hub and the inner hub.The viscous damper consists of a casing that is welded to the inner hub. The casing contains a steel weight that is suspended in a viscous silicone lubricant. The silicone lubricant acts as a flexible coupling between the weight and the inner hub.