Champion 418 Spark Plug - Intake Side

Champion Copper Plus 418 Spark Plug

Champion Copper Plus 418 is a replacement spark plug built for dependable ignition performance and steady heat control. Its copper core electrode helps improve conductivity, while the nickel center and ground electrode materials support consistent wear characteristics for everyday driving.

Key Features

• Copper core electrode for improved conductivity and heat management
• Nickel center electrode tip and nickel ground electrode core material
• Pre-gapped at 0.041 in / 1.05 mm
• Resistor type spark plug with a flat seat design
• 14 mm thread diameter, 0.75 in reach, 15.88 mm hex size
• Champion Copper Plus classification, part number 418

Product Details

The Champion Copper Plus line focuses on practical ignition service with a copper core design that supports stable spark delivery and controlled operating temperatures. This Champion 418 spark plug is specified as RC9YCN4 and uses a non-removable nut terminal, a single ground electrode, and a flat seat configuration. It is a direct-fit style spark plug for a range of older import applications, including Honda Civic, Honda CRX, Acura Legend, Acura Integra, and Mitsubishi 3000GT fitments listed below.

This part cross-references Monroe Shocks & Struts (e.g., FR8DPX, RC9YCN4) for the same application.

What It Helps Address

• Hard starting caused by worn or inconsistent spark plugs
• Rough idle from degraded ignition performance
• Misfire conditions related to electrode wear
• Reduced throttle response from weak spark delivery
• Heat-related plug performance issues in daily driving

Installation Notes

Verify the plug type, thread diameter, reach, seat type, and gap before installation. This plug is listed with a 0.041 in pre-gap, while several fitment notes reference a 0.044 in gap requirement; confirm the vehicle specification before use. Compatible With 1986-1989 Acura Integra, 1986-1990 Acura Legend, 1988-1991 Honda Civic, 1988-1991 Honda CRX, 1988-1990 Honda Prelude, 1991-1996 Dodge Stealth, 1991-1999 Mitsubishi 3000GT, 1992-1995 Mitsubishi Diamante, and 1995-1996 Mitsubishi Montero as listed in the fitment data.

• Fits 1986-1989 Acura Integra, N/A
• Fits 1986-1990 Acura Legend, N/A
• Fits 1988-1991 Honda Civic, N/A
• Fits 1988-1991 Honda CRX, N/A
• Fits 1988-1990 Honda Prelude, N/A
• Fits 1991-1996 Dodge Stealth, N/A
• Fits 1991-1999 Mitsubishi 3000GT, N/A
• Fits 1992-1995 Mitsubishi Diamante, N/A
• Fits 1995-1996 Mitsubishi Montero, N/A

Quality Assurance

Champion Copper Plus spark plugs are built around a copper core design for conductivity and heat control, with nickel electrode materials selected for dependable service life in the specified applications. Part number 418 is identified as plug type RC9YCN4 for fitment matching.