* Specific engine configuration: Was it a TBI (Throttle Body Injection), carburetor, or a different fuel injection system? Different fuel systems have different timing needs.
* Camshaft: A performance camshaft will require different timing than a stock cam.
* Engine modifications: Modifications like headers, intake manifolds, and other performance parts will also affect the ideal timing.
* Fuel octane: Higher octane fuel allows for more advanced timing.
Where to find the correct timing:
1. The owner's manual: This is the best place to start. It should list the recommended base timing for your specific engine setup.
2. A service manual: A Haynes or Chilton manual for your specific year and model will provide detailed timing specifications and procedures.
3. A decal on the vehicle: Sometimes a sticker under the hood will show the factory timing specs.
4. Data plate on the engine: The engine itself might have a data plate indicating the recommended timing. This is less common.
General advice:
* Don't just guess: Incorrect timing can damage your engine.
* Use a timing light: This is the only reliable way to accurately set your ignition timing.
* Start with the base timing: Then, use a vacuum advance if equipped and carefully adjust the timing until you achieve optimal performance and efficiency. This often involves some testing and fine-tuning. Improper adjustment can cause pinging (detonation) which is harmful to the engine.
In short, you need to identify the specific engine configuration of your 1986 350 Chevy before you can determine the correct timing. Consulting a service manual is essential for safe and accurate timing adjustment.
