* Engine condition: Worn parts, carbon buildup, and other factors affect the ideal timing.
* Fuel quality: Lower-octane fuel requires less advance to prevent detonation.
* Altitude: Higher altitudes require less timing advance.
* Modifications: Any modifications to the engine (intake, exhaust, camshaft, etc.) will change the optimal timing.
The base timing is usually specified in the owner's manual or a service manual for the vehicle. This is the starting point. However, you will need to use a timing light and adjust the timing further to find the optimal setting. This typically involves:
1. Finding the base timing specification (usually around 10-12 degrees BTDC, but check your manual). This is the timing when the engine is idling.
2. Setting the timing to the base specification using the distributor.
3. Performing a timing adjustment procedure (often using a vacuum gauge and/or a timing light while revving the engine). This step is crucial to find the best compromise between performance and preventing detonation (knocking).
Do not simply set the timing to a number you find online without going through the proper procedure. Incorrect timing can cause serious engine damage.
Recommendation: Consult a repair manual specific to your 1985 Chevy Camaro 305 TPI. This manual will provide the correct base timing and the procedure for setting and verifying the timing. If you are uncomfortable performing this task, it's best to take your vehicle to a qualified mechanic.
