* Engine Modifications: Has the engine been modified in any way? Modifications like different camshafts, heads, or intake manifolds will significantly affect the optimal timing.
* Ignition System: The type of ignition system (distributor, HEI, etc.) will influence the timing setting.
* Vacuum Advance: The vacuum advance mechanism on the distributor needs to be functioning correctly and its contribution is added to the base timing.
Instead of a specific number, the proper procedure is to:
1. Consult your owner's manual: The owner's manual should specify the *base timing* for your specific engine configuration. This is the timing with the vacuum advance disconnected.
2. Use a timing light: This is the essential tool to accurately set the timing.
3. Find the timing marks: Locate the timing marks on the harmonic balancer and the timing pointer on the engine.
4. Set the base timing: With the vacuum advance disconnected, set the engine to idle and adjust the distributor until the timing light shows the base timing specified in your owner's manual (usually around 0-10 degrees BTDC, but this is a broad range – your manual is crucial).
5. Reconnect the vacuum advance: Once the base timing is set, reconnect the vacuum advance line. The engine's timing should now advance under acceleration. You'll likely need to test drive and further fine tune the timing based on performance (smooth idle and acceleration). An improperly set timing could cause problems like poor performance, hard starting, or overheating.
Without knowing the exact engine specifications and modifications, any timing number given here would be unreliable and potentially damaging to your engine. It's strongly recommended that you consult a repair manual specific to your 1987 El Camino 305 V8 engine, or seek the assistance of a qualified mechanic.
