When you install EFI on your engine, most systems will require the ignition timing to be advanced for the ECU. This can cause issues with rotor phasing, but the new adjustable rotor remedies this issue. The rotor is based on MSD's popular PN 8467 race rotor so it will install on most any MSD distributor with a PN 8433 cap. The rotor offers up to 20 degrees of advance or retard and is easy to set up with accurate one degree increment adjustments.