20797955 Volvo.Penta Hex. socket screw

Illustration 1 g00816330
Vee engine
(1) Cylinder block
(2) Cylinder liner
(3) Filler band
(4) O-ring seals
(5) Main bearing cap
(6) Stud
(7) Nut
(8) Saddle bolt
(9) Stud
Illustration 2 g00895512
In-line engine
(1) Cylinder block
(2) Cylinder liner
(3) Filler band
(4) O-ring seals
(5) Main bearing cap
(6) Stud
(7) Nut
(8) Saddle bolt
(9) Stud
Illustration 3 g00816362
Cylinder head
(10) Nut
(11) O-ring seal
(12) Opening
(13) O-ring seal
(14) Combustion gasket Cylinder block (1) is a one-piece casting. The air inlet plenum extends for the full length of the cylinder block in order to provide even distribution of air to the cylinders.Cylinder liners (2) 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. Filler band (3) and three O-ring seals (4) seal the coolant in the cylinder block.Main bearing caps (5) are fastened to the cylinder block with two studs (6) per cap. Nuts (7) for the studs are hydraulically tensioned. Each main bearing cap has one saddle bolt (8) on each side of the cylinder block. The saddle bolts help prevent the movement of the main bearing cap. The saddle bolts also add strength to the lower area of the cylinder block.The engine has a separate cylinder head for each cylinder. Each cylinder head is fastened to the cylinder block by four studs (9) and by four nuts (10). The studs are hydraulically tensioned. The nuts are tightened by hand and the hydraulic tension is released.Each cylinder head contains the valve mechanism for inlet air, for fuel, and for exhaust gas. For information on the valve mechanism, refer to Systems Operation, "Air Inlet and Exhaust System". The inlet and exhaust valves move in replaceable valve guides which are pressed into the cylinder head.O-ring seals (11) seal coolant that flows to the cylinder head through four adapters. Engine oil that returns to the engine oil pan through opening (12) is sealed with O-ring seals (13). The seals are installed in two plates for each cylinder head.Combustion gas is sealed by combustion gasket (14) that is installed between the cylinder liner flange and the cylinder head.
Illustration 4 g00816437
(15) Cover for the camshaft
(16) Cover for the crankcase
(17) Crankcase explosion relief valve Covers (15) allow access to the camshafts, to the valve lifters, and to the valve lifter guides.Covers (16) allow access to the crankshaft, to the connecting rods, to the piston cooling jets, and to the main bearings.Crankcase explosion relief valves (17) open in order to relieve the pressure in case of an explosion in the crankcase. The valves close immediately in order to keep fresh air from entering the crankcase. A pressure of 7 kPa (1 psi) is required to open the valve. An oil screen quenches any flames from an explosion. Do not change the total number of crankcase explosion relief valves that are installed on the engine.Pistons, Rings and Connecting Rods
Illustration 5 g00816458
(1) Piston
(2) Compression rings
(3) Oil ring
(4) Connecting rod
(5) Piston pin
(6) Pin retainer
(7) Bolt
(8) Connecting rod cap
(9) Connecting rod bearing Aluminum pistons (1) have a steel crown and three rings. The rings include two compression rings (2) and one oil ring (3). All the rings are located above the piston pin bore. The oil ring is a three-piece ring. Engine oil returns to the crankcase through holes in the oil ring groove.The piston is attached to connecting rod (4) with piston pin (5) and with two pin retainers (6). The connecting rod has a taper on the pin bore end. This taper gives the connecting rod and the piston more strength in the areas with the most load. Four bolts (7) hold connecting rod cap (8) to the connecting rod. This design keeps the connecting rod width to a minimum, so that a larger connecting rod bearing (9) can be used and the connecting rod can still be removed through the cylinder liner.The piston has two 1/2 -13 NC threaded holes in the crown for lifting the piston and connecting rod assembly.Crankshaft
Illustration 6 g00816471
Typical example
(1) Journal
(2) Main bearing
(3) Thrust plates
(4) Flange The crankshaft changes the combustion forces in the cylinders into usable rotating torque which powers the driven equipment. The connecting rods for the pistons are connected to journals (1). A counterweight for each cylinder is bolted to the crankshaft.Pressurized engine oil is supplied to main bearings (2) through drilled passages in the webs of the cylinder block. The engine oil flows through passages that are drilled in the crankshaft in order to provide lubrication for the connecting rod bearings.Two thrust plates (3) control the end play of the crankshaft. Flanges (4) are machined at both ends of the crankshaft for mounting of the flywheel and of the vibration damper.
Illustration 7 g00816530
Vibration damper
The vibration damper is bolted to the front of the crankshaft in order to reduce torsional vibrations (twist) that can cause damage to the engine.
Illustration 8 g00807826
Cross sections of the crankshaft seals and wear sleeves
Seals and wear sleeve