* Early models (pre-electronic ignition): These used a distributor and mechanical advance. The timing would be set using a timing light and a degree wheel, with specifications found in a repair manual for that specific year and engine code. There wouldn't be a single number, as the advance curve would change with RPM.
* Later models (with electronic ignition and engine control unit - ECU): The ignition timing is controlled by the ECU. You cannot adjust the timing in the same way as the older cars. The ECU uses sensors (like the crankshaft position sensor and others) to determine the optimal ignition timing for different conditions. Trying to manually adjust the timing on these engines is likely to cause damage.
To find the correct timing information, you MUST consult a repair manual specific to the year and model of your Thunderbird. This manual will provide the proper procedures and specifications. Trying to find a universal timing setting is impossible and potentially harmful to your engine.
