The timing is not a single number. It depends on several factors including the engine's condition, the carburetor (or fuel injection) setup, and whether any aftermarket modifications have been made. You'll need to consult your vehicle's owner's manual or a repair manual specific to your year and model to find the recommended base timing. Even then, you'll likely need to fine-tune the timing using a timing light to achieve optimal performance and efficiency. The timing is usually set at idle.
To find the correct timing:
1. Consult your owner's manual: This is the best place to start. It will give you the manufacturer's recommended base timing.
2. Use a repair manual: A Haynes or Chilton manual for your specific vehicle will have more detailed information, including how to set the timing using a timing light.
3. A qualified mechanic: If you're uncomfortable working on your vehicle yourself, a mechanic can accurately set the timing for you.
Ignoring correct timing can lead to poor performance, reduced fuel economy, and even engine damage.