I just wanna diverge into some terminologies that you might hear the mechanic use tomorrow and feel he just wanna slide you. In automobile repair and maintenance department, various terms such as the camshaft, distributor drive and many more. I would start from painting the descriptive image of the cam shape. The reason for the compromise in the shape of the cam shape is to produce high and low engine speed coils outputs.
In a 4 cylinder engine, the dwell angle of the cam is 50°.
The distributor drive consists of the distributor spindle which is driven by the gears on the camshaft at camshaft speed, which is half of the crankshaft speed. Once the distributor is correctly adjusted, and it is timed to provide a spark at the correct point of crankshaft rotation and piston position in the cylinder.
Ignition-Timing moment which is the moment in the engine when a spark is provided in the combustion chamber to begin ignition of the fuel. This moment is know as the ignition-timing position and it varies by more than 30° of crankshaft rotation in most engines.
How to select a new plug??
The range of design details that are included in spark plug classification and identification are "code letters, or numbers, for thread diameter, length of thread(reach), design features as radio suppression, taper seat and electrode type.
Engine control module is the system in the automobile that carries out all the functions of the primary circuit, including spark generation control, and the advance and retard of the ignition timing for speed and load conditions. This system is wear-free and has high level of accuracy.