* Cam Specifications: The camshaft significantly influences ignition timing requirements. A performance cam will need different timing than a stock replacement cam.
* Engine Condition: Worn parts, carbon buildup, and other mechanical issues can affect the optimal timing.
* Fuel: The type of fuel (leaded, unleaded, octane rating) impacts the ideal timing to prevent detonation.
* Altitude: Higher altitudes require different timing adjustments.
General Guidelines:
A common starting point for a *stock* 1973 350 small-block with a 4-barrel carb is initial timing of around 8-12 degrees BTDC (Before Top Dead Center). However, this is just a starting point. You'll need to further adjust the timing using a timing light to find the optimal setting.
Finding the Optimal Timing:
To find the best timing for your specific engine, you'll need a timing light and proceed as follows:
1. Consult your engine's specifications: If you have any documentation for the engine, it might specify a recommended timing range.
2. Set the initial timing: Set the initial timing to the starting point (8-12 degrees BTDC).
3. Check for pinging (detonation): Drive the car and listen for any pinging or knocking sounds, especially under load. If you hear pinging, retard (reduce) the timing.
4. Use a vacuum advance gauge: Most distributors use a vacuum advance mechanism. This should be properly connected and operating correctly. A vacuum gauge can help to optimize this.
5. Adjust the timing for maximum performance: Once pinging is eliminated, you can fine-tune the timing by slightly advancing it (increasing the degrees BTDC) until you achieve the best combination of performance and smooth running. This often involves testing at various RPM ranges.
6. Professional Tuning: If you're not comfortable with these steps, it is best to take your vehicle to a professional mechanic for tuning.
In short: There's no magic number. You must use a timing light and adjust the timing based on the specific characteristics of your engine and its condition. Starting at 8-12 degrees BTDC is a good beginning, but further adjustment is crucial for optimal performance and reliability.
