Champion 123 Spark Plug

Champion Copper Plus RN5C Spark Plug

Champion Copper Plus 123 is a resistor spark plug built for dependable ignition performance in a wide range of classic cars and small-engine applications. Its copper core electrode improves conductivity and heat control, while the nickel center and ground electrode materials support consistent wear characteristics.

For buyers searching for a Champion 123 spark plug or an RN5C replacement, this plug is a direct match for many vintage Honda, Chevrolet, Nissan, Bentley, Volkswagen, and Lamborghini applications. It is also listed for vehicles such as the Honda Civic, Honda Accord, and Nissan 510.

Key Features

• Copper core electrode for improved conductivity and heat management
• Nickel center electrode tip and nickel ground electrode core material
• Resistor type spark plug for noise suppression in applicable systems
• Flat seat design with a removable nut terminal
• Pre-gapped at 0.025 in / 0.64 mm
• Champion Copper Plus small engine classification
• Part number 123, plug type RN5C

Product Details

Champion Copper Plus 123 is engineered around a copper-core design that helps carry current efficiently and manage combustion heat. The nickel electrode construction supports steady spark delivery and normal wear in secondary ignition systems. With a 14 mm thread diameter, 0.75 in reach, 0.813 in hex size, and flat seat, this RN5C spark plug matches the dimensional requirements called out in the fitment data. The part number 123 is commonly searched alongside RN5C and Copper Plus when replacing older ignition components.

This part cross-references Champion Spark Plug 406 and Autolite 405 for the same application.

What It Helps Address

• Hard starting caused by worn or inconsistent spark plugs
• Misfire conditions from degraded electrode surfaces
• Rough idle in older ignition systems
• Reduced spark efficiency from heat-related plug wear
• Service replacement needs for RN5C-spec applications

Installation Notes and Fitment

Compatible With 1982-1985 Lamborghini Countach, N/A; 1980-1983 Volkswagen Vanagon, N/A; 1981-1982 Honda Prelude, N/A; 1981 Honda Accord, N/A; 1975-1979 Honda Civic, N/A; 1976-1978 Honda Accord, N/A; 1975 Honda Civic, N/A; 1968-1973 Nissan 510, N/A; 1969 Chevrolet Blazer, N/A; 1969 Chevrolet C10 Suburban, N/A; 1969 Chevrolet C20 Suburban, N/A; 1969 Chevrolet K10 Suburban, N/A; 1969 Chevrolet K20 Suburban, N/A; 1967-1968 Chevrolet C10 Suburban, N/A; 1967-1968 Chevrolet C20 Suburban, N/A; 1967-1968 Chevrolet K20 Suburban, N/A; 1967 Chevrolet K10 Suburban, N/A; 1959-1965 Bentley Continental, N/A; 1952-1954 Bentley Continental, N/A.

Verify plug type RN5C, thread diameter, reach, seat style, and the specified gap for your application before installation. Gap requirements vary by vehicle, so confirm the service specification for the exact model year listed.

Quality Assurance

Champion Copper Plus plugs are built to support reliable ignition service in applications that call for a copper-core, nickel-electrode spark plug. The manufacturer description identifies this plug as a dependable-performance design with improved conductivity and heat control for good overall wear.