Introduction
The MSD 8420 Cap-A-Dapt Distributor Cap and Rotor Kit is designed to allow the use of a larger style distributor cap on your existing MSD distributor. This adaptation helps in preventing crossfire by spacing spark plug terminals farther apart, contributing to improved ignition performance and reliability.
Key Features
- Adapts a large style cap onto your MSD distributor.
- Spark plug terminals spaced farther apart to prevent crossfire.
- Retainer designed to hold plug wires securely in place.
- Constructed for incredible strength and resistance.
Figure 1: The MSD 8420 Cap-A-Dapt Kit. This image displays the complete kit, including a large red distributor cap with eight spark plug terminals and a central coil terminal, a red rotor with a metal contact arm, and a red Cap-A-Dapt adapter designed to allow the use of a larger cap on an MSD distributor. All components are branded with the 'MSD' logo.
Setup and Installation
Proper installation of the MSD 8420 Cap-A-Dapt Kit is crucial for optimal performance and safety. Always ensure the engine is off and cool before beginning any work on the ignition system.
Safety Precautions
- Disconnect the vehicle's battery before starting installation.
- Wear appropriate personal protective equipment, including safety glasses and gloves.
- Ensure the engine is completely cool to prevent burns.
Tools Required (Typical)
- Screwdriver set (Phillips and flathead)
- Wrench set (if needed for distributor hold-down)
- Dielectric grease (optional, for spark plug boots)
Installation Steps
- Preparation: Disconnect the negative battery cable. Carefully label and remove spark plug wires from the old distributor cap, noting their firing order. Remove the old distributor cap and rotor.
- Install Cap-A-Dapt Adapter: If your MSD distributor requires the Cap-A-Dapt adapter, install it onto the distributor base according to the specific instructions provided with your MSD distributor. Ensure it is seated correctly and secured.
- Install Rotor: Place the new MSD rotor onto the distributor shaft. Ensure it clicks into place or is secured by its retaining screws, depending on the distributor type. Verify it spins freely with the shaft.
- Install Distributor Cap: Align the new MSD Cap-A-Dapt distributor cap with the adapter or distributor base. Ensure the cap is seated firmly and the retaining clips or screws are securely fastened.
- Connect Spark Plug Wires: Reconnect the spark plug wires to the new cap terminals in the correct firing order, using the labels made during removal. Ensure each wire is fully seated.
- Final Check: Double-check all connections and ensure no tools or debris are left in the engine bay. Reconnect the negative battery cable.
Note: For detailed distributor-specific installation, refer to your MSD distributor's instruction manual.
Operating Principles
The MSD 8420 Cap-A-Dapt Kit functions as a critical component within your vehicle's ignition system. Its primary role is to distribute high voltage from the ignition coil to the correct spark plug at the precise moment for combustion.
The distributor cap houses the terminals for the spark plug wires and the central coil wire. The rotor, mounted on the distributor shaft, spins inside the cap, making contact with the central coil terminal and then sequentially passing close to each spark plug terminal. This action allows the high voltage spark to jump the small air gap to the correct spark plug wire, initiating combustion in the corresponding cylinder.
The Cap-A-Dapt design, with its wider terminal spacing, is specifically engineered to minimize the risk of "crossfire," where the high voltage spark jumps to an adjacent terminal prematurely. This ensures a cleaner, more efficient spark delivery, which can contribute to smoother engine operation and improved performance.
Maintenance
Regular inspection and maintenance of your MSD Cap-A-Dapt Kit will ensure its longevity and continued optimal performance. While the kit is designed for durability, wear and tear can occur over time.
Inspection Schedule
- Inspect the distributor cap and rotor every 15,000 to 30,000 miles, or as recommended by your vehicle's service manual.
- Check for cracks, carbon tracking (black lines), corrosion on terminals, or excessive wear on the rotor tip.
- Ensure spark plug wires are securely connected and free from damage.
Cleaning and Care
- If minor carbon deposits are present, they can often be carefully wiped away with a clean, dry cloth.
- Do not use harsh chemicals or abrasive materials, as these can damage the cap or rotor.
- Ensure the cap and rotor are completely dry before reinstallation.
Replacement
If significant wear, cracks, or carbon tracking are observed, the cap and rotor should be replaced. These components are wear items and will eventually require replacement to maintain proper ignition system function.
Troubleshooting
If you experience ignition-related issues after installing or while using the MSD 8420 Cap-A-Dapt Kit, consult the following common troubleshooting steps:
| Symptom | Possible Cause | Solution |
|---|---|---|
| Engine Misfire / Rough Idle | Damaged or worn cap/rotor, incorrect spark plug wire routing, carbon tracking. | Inspect cap and rotor for damage. Verify correct firing order and secure wire connections. Clean or replace components as needed. |
| Engine Cranks but Won't Start | No spark, severely damaged rotor or cap, loose coil wire. | Check for spark at the plugs. Ensure coil wire is securely connected to the cap. Inspect cap and rotor for severe damage. |
| Poor Engine Performance / Reduced Power | Degraded cap/rotor, crossfire due to worn components. | Inspect cap and rotor for signs of wear or carbon tracking. Consider replacement if components show significant degradation. |
| Visible Arcing / Spark Jumps | Cracked cap, carbon tracking, excessive moisture. | Replace the cap if cracked. Ensure the cap is clean and dry. |
If issues persist after troubleshooting, it is recommended to consult a qualified automotive technician or contact MSD technical support.
Specifications
| Attribute | Detail |
|---|---|
| Brand | MSD |
| Model Name | MSD 8420 Cap-A-Dapt Distributor Cap and Rotor Kit |
| Part Number | 8420MSD |
| OEM Part Number | 8420 |
| Color | Red |
| Material | Plastic |
| Item Weight | 1.3 Pounds |
| Closure Type | Twist-On |
| Item Package Dimensions L x W x H | 10.63 x 10.04 x 8.11 inches |
| Manufacturer | MSD Ignition |
| UPC | 085132084203 |
| GTIN | 00085132084203 |
| Vehicle Service Type | Car |
Warranty Information
MSD products are manufactured under strict quality control standards. The MSD 8420 Cap-A-Dapt Kit comes with a manufacturer's warranty. For specific details regarding the warranty period, coverage, and claims process, please refer to the official warranty documentation included with your product or visit the MSD Ignition website.
Note: Warranty terms may vary based on region and point of purchase. Retain your proof of purchase for warranty claims.
Customer Support
For technical assistance, installation questions, or troubleshooting beyond the scope of this manual, please contact MSD Ignition customer support.
- Online Resources: Visit the official MSD Ignition website for FAQs, additional manuals, and technical bulletins.
- Contact Information: Refer to the MSD Ignition website or product packaging for the most current contact details, including phone numbers and email addresses for technical support.
When contacting support, please have your product model number (8420MSD) and any relevant purchase information readily available.
