- Initial ignition timing for a 1970 402 big block Chevy should be set to 4 to 6 degrees Before Top Dead Center (BTDC).
Total Ignition Timing:
- The maximum, or total, ignition timing for this engine should be set to approximately 36 to 38 degrees BTDC at about 3000 RPM.
Vacuum Advance:
- Vacuum advance should provide an additional 10 to 12 degrees of timing advance at idle, which is then disconnected and plugged during high RPM operation.
Note that these are general guidelines, and the optimal ignition timing for your specific engine may vary depending on several factors, including engine modifications and fuel type. It's always best to consult a trusted mechanic or refer to a reliable source for the exact timing specifications for your vehicle.
