[Jack21]

Your timing should be unaffected by adding a PCV.

Your primary side jetting may need to be increased a size or two because you're adding additional air with the PCV. Idle mixture may need resetting. Secondaries should not need any changes as PCV adds little, if any air under low vacuum, such as when secondaries are open.

If you don't re-jet, and engine starts pinging, re-jet carb before retarding timing.