Engine Reassembly (Automobile)


Engine Reassembly

First the reassembly of the upper engine parts is discussed. The parting surfaces of the head and block should be re-cleaned. The new head gasket is checked for proper fit. Until unless marked as top or front, the gasket identifica­tion numbers go against the head
Head gasket position marking.
Fig. 20.143. Head gasket position marking.
Cylinder Head Installation
Fia 9.0 144 Cylinder Head Installation
(Fig. 20.142.). All of the head cap screws are installed finger tight. The head cap screws must be torqued following an exact sequence as given in the service manual, so as to form a good seal and eliminate warpage. In general, the centre cap screws are torqued first. Cap screws adjacent to the centre are tightened next. This procedure is continued until the end cap screws are tightened. It is the usual practice to go through the torque sequence twice. The first time, the
Torque the head cap screws during assembly.
Fig. 20.145. Torque the head cap screws during assembly.
Pushrod and rocker arm installation.
Fig. 20.146. Pushrod and rocker arm installation.
cap screws are torqued to half the specified torque value and the second time to full torque value. Even some technicians follow the sequence a third time to ensure proper torque. The torque sequence is shown in Fig. 20.144 and head cap screw torque in Fig. 20.145.
The pushrods, rocker arms, and pivots are installed next. The valve train is assembled and adjusted before the manifold is installed so that the entire valve system can be observed for correct assembly. Special care should be taken to correctly position the push rods. Some push-rods have hardened ends that are put at the rocker arm end. Some engines have different length push-rods on the intake and exhaust valve trains. The rocker arm pivot bolts are torqued to the specified torque with the timing gears in positions A and B of Fig. 20.146. The timing gears are installed in position A, and position B is obtained by turning the engine one revolution. The entire rocker arm installation and their pivot bolt torque sequence is illustrated in Fig. 20.144.
If the valve train is adjustable, the adjustment can best be achieved before the manifold is installed. The hydraulic lifters are positioned in the middle of their travel. It allows observing the lifter as the adjustment is being carried out. Engines having no valve train adjustment are set during the valve job by correctly positioning the valve tip height. Valve trains must be adjusted before the engine is started.
Some service manuals provide a specific sequence to be used to adjust the valve train. The following procedure, however, is applicable for any engine having valve lash adjustment. The engine is turned in the normal direction of rotation until both valves on number one cylinder are closed and the top centre timing mark aligns. At this crankshaft position, the valves are adjusted. Hydraulic valve lifters are adjusted until the clearance is not seen. This can be observed by looking at the lifters with the manifold still off the engine. The adjustment is tightened the specified amount to centre the plunger in the lifter bore (from one-half to one-and-a-half turns more). Solid lifter systems are adjusted 0.05 mm greater than the specified clearance. This is very close to the correct valve lash on the warmed up engine.
Intake manifold installation.
Fig. 20.147. Intake manifold installation.
The engine is turned in the normal direction of rotation to the next cylinder in the firing order (90 degrres on eight cylinder engines, 120 degrees on six cylinder engines, andl80 degrees on four cylinder engines), and the valves on this cylinder are adj usted. This procedure is repeated in the firing order until all the the valves have been adjusted. The technician usually does a second time valve lash check on solid lifter engines to make sure that the earlier lash adjustment has been done correctly. Once the valves are adjusted, the manifolds can be installed.
The manifold parting surfaces are wiped clean. The gasket is coated with sealer if sealer is to be used and then placed on the head and block parting surfaces. It must be ensured to properly position the intake manifold gasket lap on V-engines in the corner of the head and lifter valley. The manifold is carefully lowered into position, and the gaskets must not move as the manifold seats. The manifold cap screw threads are applied with sealer to help prevent coolant leaks. In some manifolds, the screws must be of a specified length to hold securely. Similar to heads, the intake manifold’s cap screws are torqued in the sequence given in Fig. 20.147 to form a secure seal.
Some exhaust manifolds use gaskets while others do not. Exhaust gaskets are always installed dry. The exhaust manifold’s screws are torqued in the sequence given in Fig. 20.148. Exhaust leaks produce unnecessary noise and, in some engines, disturb the correct functioning of the emission controls. It is a general practice to use new belts, hoses, a tune-up, oil change, and antifreeze with the valve job while the engine is reassembled.
Exhaust manifold installation.
Fig. 20.148. Exhaust manifold installation.
The valve train does not require a break-in. When the engine is running and warmed up, the solid lifter valve lash is checked and adjusted, then the rocker arm covers are secured. With the engine completely assembled, it is checked for leaks. If the engine exterior is dry, the automobile can be delivered to the customer, if only upper engine service is necessary.
Now the reassembly of lower engine parts is discussed. The first step, as usual, is a final, thorough cleaning to remove any dust or dirt from the parts. Gasket sealing compound is put on the edge of the core plugs and all screw plugs are installed in the block. The camshaft is liberally coated with the recommended lubricant, and carefully put in place, taking enough care not to score the cam bearings or to knock the plug from the rear of the camshaft bore. To avoid this some manufacturers use a special cam holding tool and others depend on thrust plate.
Rear main bearing gasket and seal installation.
Fig. 20.149. Rear main bearing gasket and seal installation.
The rear main oil seal is installed prior to the replacement of the crankshaft (Fig. 20.149). Rope-type seals are packed into the seal groove. The crankshaft and new main bearings are lubricated with SE motor oil. The crankshaft and bearing caps are installed, the thrust bearings aligned as illustrated in Fig. 20.150, and then the caps are torqued.

The crankshaft turning effort should be checked with a torque wrench after each cap is tightened. If the turning effort increases appreciably after one cap is tightened, then that cap
Seating the thrust bearings before tightening the main bearing caps by moving the crankshaft endwise with a pry.
Fig. 20.150. Seating the thrust bearings before tightening the main bearing caps by moving the
crankshaft endwise with a pry.
should be removed and the cause of binding determined. This procedure of measuring turning effort should be followed throughout engine assembly. This helps to repair any tight spots or binding immediately before any further assembly is carried out. All gaskets and seals around
Timing gear and chain installation.
Fig. 20.151. Timing gear and chain installation.
Timing gear cover and gasket installation.
Fig. 20.152. Timing gear cover and gasket installation.
the rear main bearing cap must be correctly installed, following special instructions for that specific type of engine, if any.
Cam gears, sprockets, and chains are aligned and installed. During installation of timing gears and chain, the timing marks on the gears must be aligned (Pig. 20.151). Gear or chain backlash should be rechecked to confirm that it is within limits. A hew oil seal is used in the
Sealant applied to timing gear cover.
Fig. 20.153. Sealant applied to timing gear cover.
 Oil pan installation.
Fig. 20.154. Oil pan installation.
timing cover. In case a slingler ring is used, it is installed on the crankshaft followed by the timing cover with a new gasket. The gasket is usually coated with a non-hardending gasket compound. The crankshaft damper is installed prior to the tightening of the timing cover, so that the oil seal and timing cover are properly centred themselves on the damper hub. The cover is then tightened to the correct torque. Timing gear cover and gasket installation are shown in Fig. 20.152. Piston assembles are carried out in the manner previously described.
Some timing gear covers use a room-temperature vulcanizing (RTV) sealer and an anaerobic sealer in place of the gasket (Fig. 20.153).
Oil pump gears are provided with a light coating of heavy oil or light grease to provide initial lubrication that causes the pump to prime itself. The pump is installed with new gaskets and seals. In some engines, the oil pump drive rod must be installed as the pump is installed. Windage trays or baffles are installed, if they are used.
Oil pan seals are carefully placed in position for proper sealing. The pan is installed and the retaining bolts snugged up, then torqued (Fig. 20.154).
This completes the assembly of the lower-engine. The heads, valve train, and manifolds are assembled and adjusted as already described in this section. When the basic engine is completely assembled, the clutch and transmission are installed as described in respective chapters.
The oil filter is put on the engine and the crankcase filled with the correct quantity and quality of engine oil. It is the right time to check the functioning of the lubricating systems before the engine is installed in the chassis and started. Oil pressure failure can damage the new bearings and journals. The oil pump is driven by hand using a properly fitting small socket, screwdriver, or hex rod, whichever is applicable. A socket speed handle is attached to rotate the pump. Using a drill motor to rotate can score the pump before oil pressure develops and cause
Distributor and spark plug wire installation.
Fig. 20.155. Distributor and spark plug wire installation.
premature failure of the oil pump. Turning the pump by hand in the correct direction takes about 30 seconds to fill the filter and develop oil pressure. If pressure is not developed, the cause is determined and corrected, while the engine is still out of the chassis.
It is a good practice to replace the engine mounts with new mounts before the engine is reinstalled. This also takes care of all the fatigued and worn out mounts. The hoisting sling is installed, and the engine is lowered into the chassis, keeping transmission end first.
The assembly of the underside of the engine is taken up first. This includes clutch and transmission controls, the speedometer cable, propeller shaft, steering linkages, and exhaust pipe. Then on the top side of the engine the radiator, thermostat and air conditioner are installed. Normally all coolant hoses and all belts are replaced to ensure maximum period before this service is taken up again.
The carburettor, fuel pump, filter, and fuel lines are installed. All emission control units, instrument senders, and lines are properly connected. Other components like distributor, spark plugs, and plug wires are installed.
The starter and alternator are installed and the connecting wires secured. The fully charged battery should be installed to crank the engine while timing the ignition. The engine crankshaft is positioned at top centre on the compression stroke of number one cylinder. The distributor is positioned to fire number one spark plug, and then it is installed in the engine. While installing the distributor, the rotor must be pointing towards the plug wire connected to the piston on the compression stroke. This is the number 1 or 4 piston depending on whether one is dealing with timing gear position A or B (Fig. 20.146). With the rotor in the correct position, the high point on the armature must be aligned with the pick-up coil. The correct distributor position and spark plug wire installation are shown in Fig. 20.155.
All installation connections should be rechecked, the coolant system filled, and the hood replaced.

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