Cylinder Block, Liners And Heads
The main bearing caps are fastened to the block with two bolts per cap.
The cylinder liners can be removed for replacement. The top surface of the block is the seat for the cylinder liner flange. Engine coolant flows around the liners in order to keep the liners cool. Three O-ring seals around the bottom of the liner make a seal between the liner and the block. A filler band at the top of each liner forms a seal between the liner and the cylinder block.
A steel spacer plate is used between the cylinder head and the block. A thin gasket is used between the plate and the block to seal water and oil. A thick gasket of metal and asbestos is used between the plate and the head to seal combustion gases, water and oil.
The engine has a single, cast head on each side. Two intake valves and two exhaust valves are controlled by a pushrod valve system. These four valves are in each cylinder. The opening for the spark plug adapter is located between the four valves. Series ports are used for both the intake and the exhaust valves.
The valve lifters may be removed while the head is installed. This is because of the size of the pushrod openings.
Valve guides that do not have shoulders are pressed into the cylinder head.
Pistons, Rings And Connecting Rods
The piston has three rings. There are two compression rings and one oil ring for each piston. One of the compression rings is the top ring. The other compression ring is the intermediate ring. The rings are located above the piston pin bore. The compression ring seats in an iron band which is cast in the piston. The oil ring is spring loaded. External cast notches in the oil ring groove return oil to the crankcase.
The full floating piston pin is held in place by two snap rings. The snap rings fit in grooves that are in the pin bore.
The connecting rod has a taper on the pin bore end. This gives strength to the rod and the piston. Added strength is needed in the areas with the most load.
An oil spray is provided through jets that are located on the cylinder block main webs. This oil spray is directed to the piston components and the cylinder walls. This oil provides cooling and lubrication.
Cooling for gallery pistons is provided by two jets per cylinder. One jet for cooling cools the piston under the piston crown. The other jet for cooling directs oil into a cast gallery behind the piston rings.
The crankshaft changes the combustion forces in the cylinder. These forces are changed into the usable rotating torque that powers the machine. This vibration may be caused by impacts from combustion along the crankshaft. This vibration is kept to a minimum by a vibration damper on the front of the crankshaft.
The vibration damper is a gear at the front of the crankshaft. This gear drives the timing gears and the oil pump. Lip seals and wear sleeves are used at both ends of the crankshaft. The lip seals and the wear sleeves provide easy replacement. Pressure oil is supplied to all bearing surfaces through drilled holes in the crankshaft. The crankshaft is supported by five main bearings in 3408 engines. The crankshaft is supported by seven main bearings in the 3412 engines. There is a thrust plate at either side of the center main bearing. This thrust plate controls the end play of the crankshaft.
The engine has a single camshaft that is driven at the front end of the engine. The camshaft is supported by five bearings in the 3408 engines. The camshaft is supported by seven bearings in the 3412 engines. As the camshaft turns, each cam moves two valves. The cam moves either two exhaust valves or two intake valves for each cylinder. The camshaft gear must be timed to the crankshaft gear. Proper timing of the valves in each cylinder is dependent upon the relation of the cams to the camshaft gear.
A gear on the rear of the camshaft is used to drive the balancer gear on 3408 engines.
Regular power impacts along the length of the crankshaft cause twisting in the crankshaft. This twisting of the crankshaft is torsional vibration. The fluid type vibration damper is installed on the front end of the crankshaft. The vibration damper is used for the reduction of torsional vibrations. This also stops the vibration from building up to amounts that may cause damage.