Caution: Broken valve springs and damaged valve stem seals can be replaced without removing the cylinder head. This operation usually requires special tools and a source of compressed air, so please read this section carefully and purchase or rent the necessary tools before proceeding. If you do not have a source of compressed air, a piece of nylon rope can be used to prevent the valves from falling into the cylinder during this work.
Remove the cover from the cylinder head.
Remove the camshafts and tappets or axles with rocker arms.
Remove all spark plugs.
Rotate the crankshaft so that the desired cylinder is at TDC on the compression stroke. When replacing all valve stem seals, start with the first cylinder and work on each cylinder in turn. Move from cylinder to cylinder in ignition order (1-3-4-2).
Screw the adapter into the spark plug hole and connect the compressed air hose to it. In many specialized auto shops, such an adapter can be purchased. Many in-cylinder compression testers use a screw-in adapter, which can be installed in this case.
Direct compressed air into the cylinder.
Caution: The piston can be pushed down with compressed air, causing the crankshaft to rotate unexpectedly. If the key used to set the first piston to TDC. is still attached to the bolt at the front end of the crankshaft, it could cause injury if the crankshaft turns unexpectedly.
Valves must be held in place with compressed air. If the valve or seat surfaces are in poor condition, leaks can prevent compressed air from holding the valves - refer to the alternative method below.
If you do not have a source of compressed air, an alternative method can be used. To do this, set the piston just before TDC on the compression stroke, then run a long piece of nylon string through the spark plug hole until it fills the combustion chamber. Be sure to leave the end of the rope hanging from the motor so it can be easily removed. Using a large wrench, turn the crankshaft in the normal direction of rotation until a slight resistance is felt.
Place a clean rag in the cylinder head holes above and below the valves to prevent parts and tools from falling into the engine, then use a spring compression tool. Remove the valve cotters with small pointed pliers or a magnet.
Remove the spring cap, valve springs, then remove the valve guide seal. Valves should be held in place with compressed air. If the valve or seat surfaces are in poor condition, leaks can prevent compressed air from holding the valves - refer to the alternative method below.
If you do not have a source of compressed air, an alternative method can be used. To do this, set the piston just before TDC on the compression stroke, then run a long piece of nylon string through the spark plug hole until it fills the combustion chamber. Be sure to leave the end of the rope hanging from the motor so it can be easily removed. Using a large wrench, turn the crankshaft in the normal direction of rotation until a slight resistance is felt.
Place a clean rag in the cylinder head holes above and below the valves to prevent parts and tools from falling into the engine, then use a spring compression tool. Remove the valve cotters with small pointed pliers or a magnet.
Remove the spring cup, valve springs, then remove the valve guide oil seal.
Valve fittings
1 - spring seat (bottom plate);
2 - stuffing box (oil cap);
3 - spring;
4 - top plate;
5 - crackers.
Caution: If compressed air pressure does not hold the valve closed during this operation, it is likely that the valve face or seat is damaged. If this is the case, then the cylinder head will have to be removed for repair.
Wrap a rubber band or film around the top of the valve stem to keep the valve from falling into the combustion chamber, then cut off the air supply to the engine cylinder.
Caution: If nylon rope was used instead of air pressure, turn the crankshaft slightly in the opposite direction of normal rotation.
Check the valve stem for damage. Rotate the valve in the guide and check for movement of the eccentric at the end, which would indicate that the valve is bent.
Move the valve up and down in the guide sleeve and make sure it does not get stuck. If the valve stem sticks, either the valve is bent or the valve guide is damaged. In any case, it is necessary to remove the head for repair. • Reapply air pressure to the cylinder to hold the valve closed, then remove the rubber band or film from the valve stem. If nylon rope was used, turn the crankshaft in the direction of normal rotation until you feel a slight resistance.
Install the springs over the valve.
Lubricate the valve stem with engine oil and install a new oil seal.
Install the spring mount (crackers). Compress the spring with a puller and carefully insert the crackers into the groove. Apply a little grease to the inside of each cracker to hold it in place.
Depressurize the compressor and make sure the nut is properly seated.
Tap the valve with a rubber mallet.
Disconnect the compressed air hose and remove the adapter from the spark plug hole. If nylon rope was used instead of compressed air, remove it from the cylinder.
Install camshafts, tappets or rocker arms.
Install spark plugs and connect high voltage wires.
Install the cylinder head cover.
Start the engine and let it run, then check for leaks and/or unusual noises coming from under the valve cover.
Installing the oil seal with a tool