This is the static setting of the distributor or engine management system before any mechanical, vacuum, or electronic advance mechanisms alter the spark delivery. It is measured in degrees before top dead center on the compression stroke. Setting this correctly ensures the engine idles properly and provides a known zero-point for the dynamic timing curve to build upon as RPM and engine load increase.
Disconnect the vacuum advance hose and plug it before you put the light on it to check the basic ignition timing.
Also heard as
- base timing
Related terms
Ignition timing
The exact moment a spark plug fires relative to the position of the piston during the compression stroke.
Dynamic ignition timing
The continuous adjustment of spark delivery by an engine computer while the vehicle is running.
Top dead center
The exact point in engine rotation where a piston reaches its highest position in the cylinder.
Computer-controlled timing
An ignition system where an electronic control unit determines exactly when to fire the spark plugs.