* Engine modifications: Modifications like camshafts, headers, and carburetor changes significantly affect ignition timing.
* Fuel type: The type of gasoline (leaded, unleaded, octane rating) will influence the ideal timing.
* Engine condition: Wear and tear on the engine can affect performance and the best timing.
* Vacuum advance: The vacuum advance mechanism itself can vary in effectiveness.
Instead of a specific number, you should consult your owner's manual. This manual will give you the *base* timing (usually specified at idle, with the vacuum advance disconnected). Even then, that's just a starting point. You'll likely need to fine-tune it using a timing light and following a procedure to dial it in for best performance and to avoid damaging your engine.
To find the optimal timing:
1. Consult the owner's manual: This is the first and most important step. It should specify the base timing.
2. Use a timing light: This is the tool you'll need to check and adjust the timing.
3. Follow a procedure: There are many resources online and in repair manuals that detail how to correctly set timing using a timing light, including connecting and disconnecting the vacuum advance.
Trying to find a single number online without considering the specifics of your particular engine is risky. Incorrect ignition timing can lead to poor performance, reduced fuel economy, engine damage, or even catastrophic failure. Proceed carefully and consult reputable resources.
