* Year of manufacture: The specifications changed slightly over the years the 250 was produced.
* Engine modifications: Any alterations to the engine (camshaft, carburetor, etc.) will significantly impact ideal timing.
* Fuel type: The type of fuel used will influence the best ignition timing.
* Condition of the engine: Wear and tear can affect optimal timing.
Therefore, there's no single "correct" answer. You absolutely *cannot* rely on a generic number found online.
To find the correct timing:
1. Consult your owner's manual: This is the most reliable source of information for your specific engine. It will provide the factory-recommended initial timing setting.
2. Use a timing light: This is the only accurate way to check and adjust your ignition timing. You'll need to find the timing marks on your engine's harmonic balancer (or damper) and the timing pointer. The owner's manual or a repair manual for your specific year and model will show you how to do this.
3. Fine-tune with a vacuum gauge: After setting the initial timing, you can use a vacuum gauge to further optimize it for best engine performance and fuel economy. A higher vacuum reading generally indicates better timing.
4. Consider a professional mechanic: If you're not comfortable working on your engine, taking it to a qualified mechanic is the safest option. They'll have the tools and expertise to accurately set the timing.
In short, looking for a specific number without considering the above factors is dangerous and could damage your engine. Always refer to your owner's manual or a repair manual specific to your Chevy 250's year and model.
