MSD 8421 Adjustable Distributor Rotor Assembly Cap-A-Dapt

The MSD 8421 Adjustable Rotor Assembly is a performance distributor rotor designed for MSD distributors that gives you precise control over rotor phasing. Unlike fixed rotors, this unit allows you to adjust the rotor tip-to-cap terminal alignment to dial in optimal timing accuracy — an essential capability when running advanced timing control strategies.

Key Features:

• Fully adjustable rotor phasing — fine-tune the rotor tip alignment to match your timing setup
• Based on MSD's popular PN 8467 Race Rotor design for proven performance
• Stainless steel contact terminal for reliable spark transfer and long service life
• Spark plug-style cap terminals provide tight, vibration-resistant connections
• Ideal for use with MSD Atomic TBI systems where the ECU controls ignition timing
• Essential when running a Multi-Step Retard or Timing Controller that changes timing significantly
• Legal for use on emissions-controlled vehicles, non-emissions vehicles, and racing applications
• Sold individually

All MSD distributors are phased at the factory, but when a timing controller or Atomic TBI system takes over ignition timing duties, the rotor phasing may need to be recalibrated. The MSD 8421 makes that adjustment straightforward, ensuring the rotor tip aligns correctly with the cap terminal at every timing degree. Backed by MSD's one-year warranty against defects in materials and workmanship.