VALVE TIMING (fig. 2-26) is a system developed
for measuring valve operation in relation to crankshaft
position (in degrees), particularly the points when the
valves open, how long they remain open, and when they
close. Valve timing is probably the single most
important factor in tailoring an engine for special needs.
An engine can be made to produce its maximum power
in various speed ranges by altering valve timing. The
following factors together make up a valve operating
Figure 2-26.Typical valve timing diagrams.
Figure 2-27.Opening and closing points of the valve.