861716 Volvo.Penta Adjusting screw

Cylinder Head Assembly
The cylinder head is a one-piece cast iron head. The camshaft is contained within the cylinder head. This improves the rigidity of the valve train. Steel reinforced aluminum bearings are pressed into each journal. The bearings are lubricated under pressure. Bridge dowels have been eliminated as the valve train uses floating valve bridges.Thermal efficiency is enhanced by the use of stainless steel thermal sleeves in each exhaust port. The sleeves reduce the amount of heat rejection to the cooling system. The sleeves then transfer the thermal energy to the turbocharger.The electronic 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
One-Piece Pistons
The piston is a one-piece design that is forged steel. The pistons are cooled by engine oil. The engine oil is sprayed into the cooling chamber of the pistons by the piston cooling jets. The cooling chamber for the piston is formed by the lip that is forged at the top of the piston and the cavity that is behind the ring grooves. The pistons have three rings that are located in grooves in the crown of the piston. The rings seal the combustion gas and the rings prevent excessive amounts of engine oil from entering the combustion chamber. The top ring has a Physical Vapor Deposition (PVD) coated barrel face. This ring is a KEYSTONE ring. The second ring is the intermediate ring. The intermediate ring has a tapered rectangular face with a chrome coating. The third ring is the oil ring. The oil ring is double railed and the ring is ground with a profile. This ring is also coated with chrome. The oil 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 drain excess oil from the oil ring. The connecting rod is a conventional machined cap design. The cap is secured to the connecting rod by four bolts that are threaded into the connecting rod. There is a lubricant passage that is machined through the shank of the connecting rod in order to provide engine oil to the piston pin.Crankshaft
The crankshaft converts the combustion force in the cylinder into rotating torque. The rotating torque powers the equipment. On this engine, a vibration damper is used at the front of the crankshaft in order to reduce the torsional vibrations. The torsional vibrations can cause damage to the engine.The crankshaft drives a group of gears (front gear train) on the front of the engine. The front gear train provides power for the following components: camshaft, water pump, oil pump, air compressor and other accessories.The crankcase has seven main bearings that support the crankshaft. The crankcase also has two bolts which hold each bearing cap to the block. The oil holes in the shell for the upper bearing are located at all of the main bearing journals. The grooves in the shell for the upper bearing are also located at all of the main bearing journals. The holes and the grooves supply oil to the connecting rod bearings. The crankshaft has eight counterweights which are forged integrally. The eight counterweights are located at cheeks 1, 2, 5, 6, 7, 8, 11 and 12.To seal the crankcase, crankshaft seals are installed in the front timing gear housing and the flywheel housing.Camshaft
The camshaft has three lobes for each cylinder. These lobes allow the camshaft to operate the electronic unit injectors, exhaust valves, and the inlet valves. The camshaft is supported in the cylinder head by seven journals which are fit with aluminum bearings. A bearing is pressed into each journal. The camshaft gear contains integral roller dampers that counteract the torsional vibrations that are generated by the high pressure from operation of the electronic unit injectors. The design reduces gear train noise. This design also increases the life of the gear train. The camshaft is driven by an adjustable idler gear which is turned by a fixed idler gear which is turned by a cluster idler gear in the front gear train. Each bearing journal is lubricated from the oil manifold in the cylinder head. A thrust plate that is located at the front positions the camshaft. Timing of the camshaft is accomplished by aligning marks on the crankshaft gear and idler gear.