Ignition timing is preset and cannot be adjusted. Ignition timing is controlled by the Powertrain Control Module (PCM).
On V6 motors the distributor is located in a fixed, non-adjustable position. DO NOT attempt to rotate the distributor otherwise damage may result.
On V8 engines the distributor can be rotated for proper alignment of the rotor to the cap. The engine base timing is not adjustable by rotating the distributor.