Your 63 mercury monterey 390 backfires during cold start?

Backfiring during a cold start in your 1963 Mercury Monterey with a 390 engine could be due to several issues. Common causes include a rich fuel mixture, ignition timing being off, or a malfunctioning choke that isn’t closing properly, leading to an improper air-fuel ratio. Additionally, check for vacuum leaks or spark plug problems, as these can also contribute to backfiring. It's advisable to inspect these components to identify and resolve the issue.