If you received it from repair after valve maintenance, then the valves and related items are already in place, and if not, then:
Install the valve in its original place.
Install the spring seat, spring seal and top plate.
Valve fittings
1 - spring seat;
2 - stuffing box (oil cap);
3 - spring;
4 - top plate.
Install the tool and compress the valve springs so that the valve groove is visible.
Install crackers on the upper groove of the valve and release the springs by releasing the tool.
Siege crackers with a blow of a rubber mallet on the valve plate.
Repeat the above procedure for all other valves. Be sure to install all the components in their original places - do not mix them up!
Check the set height of the valve springs using a special ruler or measuring device. If the head was repaired in a workshop, then the set height of the springs must correspond to the required value (however, check it again). The measurement is taken from the top of each spring seat to the bottom of the mount. If the height is not correct, additional washers must be installed.
Further assembly of the head is carried out in reverse order.