* Engine specifics: The exact engine code (found on the engine block) will dictate some variations. Different camshafts, compression ratios, and carburetor setups will all affect optimal timing.
* Distributor type: The type of distributor (HEI, points, etc.) will influence the base timing.
* Engine condition: Wear and tear on the engine can affect the ideal timing.
Instead of searching for a single number, you need to consult your owner's manual or a reputable repair manual specific to your 1975 454's engine code. These manuals will provide the *base timing* and instructions on how to adjust it using a timing light. You'll likely need to adjust the timing based on your engine's specific needs and running conditions.
Generally speaking, the base timing for a 1975 454 might be in the range of 8-12 degrees BTDC (Before Top Dead Center) at idle. However, this is just a very rough estimate. Do not rely on this number; consult your manual. Improper timing can lead to reduced performance, poor fuel economy, and even engine damage.
