* Engine RPM: The ignition timing advances with increasing engine speed.
* Engine Load: The timing is also affected by the load on the engine (e.g., acceleration vs. cruising).
* Vacuum Advance: A vacuum advance mechanism on the distributor adjusts timing based on engine vacuum.
Therefore, you can't find a simple "X degrees BTDC" answer. Instead, you need to:
1. Consult a factory service manual: This is the best source for the correct procedure. The manual will guide you through setting the base timing and verifying the operation of the vacuum and centrifugal advance mechanisms. It might provide a base timing specification (often around 0-10 degrees BTDC), but this is only a starting point.
2. Use a timing light: This tool is essential for setting the ignition timing correctly. It will allow you to see the timing mark on the harmonic balancer relative to the timing pointer on the engine. The service manual will show you how to properly connect the timing light and where to find the timing marks.
In short: Don't try to find a single number. Use a factory service manual and a timing light to set the ignition timing correctly. Improper timing can cause poor performance, reduced fuel economy, and even engine damage.
