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 sequence:

Figure 2-26. - Typical valve timing diagrams.

Figure 2-27. - Opening and closing points of the valve.