Autolite 403 Spark Plug

Autolite 403 Copper Resistor Spark Plug

Autolite 403 is a copper resistor spark plug built for OE-style fit, form, and function across a wide range of classic and older import and domestic applications. It is a practical choice for drivers looking for reliable starting, steady idle quality, and smooth throttle response.

The Copper Resistor Spark Plug line focuses on everyday drivability and value, with a copper center electrode, nickel tip materials, and a 5,000 ohm resistor design for ignition noise control. For fitment-based searches, this part is commonly referenced for Volkswagen Vanagon, Honda Accord, Honda Prelude, Honda Civic, Porsche 911, and Chevrolet Corvette applications.

Key Features

• Autolite part number 403
• Copper center electrode with nickel center and ground electrode tip materials
• 5,000 ohm resistor design
• Pre-gapped at 0.034 in. / 0.90 mm
• 14.0 mm thread diameter, 0.750 in. reach, flat seat
• 13/16 in. hex size with removable nut terminal
• Ceramic insulator with short insulator type
• OE-style spark plug construction for a broad range of foreign and domestic vehicles

Product Details

Autolite 403 is a standard copper resistor spark plug engineered around OE-style dimensions and ignition performance. The copper core supports consistent spark delivery, while the resistor helps reduce electrical interference in the ignition system. With a tapered ground electrode tip design and a pre-set gap of 0.034 in., this plug is suited to maintenance work where correct heat transfer, stable combustion, and factory-style fitment matter. It is a direct search match for applications such as Fits 1990-1991 Volkswagen Vanagon, N/A; Fits 1983-1988 Volkswagen Vanagon, N/A; Fits 1980-1983 Honda Accord, N/A; Fits 1981-1982 Honda Prelude, N/A; Fits 1980 Honda Civic, N/A; and Fits 1972-1977 Porsche 911, N/A. This part cross-references Autolite 104 for the same application.

What It Helps Address

• Hard starting caused by worn or fouled spark plugs
• Rough idle and inconsistent combustion
• Reduced throttle response from aged ignition components
• Ignition noise concerns in resistor-equipped systems
• Maintenance replacement for OE-style spark plug service

Installation Notes

Verify the vehicle’s specified gap, thread reach, seat type, and terminal style before installation. The plug is pre-gapped at 0.034 in. / 0.90 mm, but final gap should always be checked against the application requirements listed for the vehicle. Use the correct torque procedure for the cylinder head material and inspect the ignition wires or coil boots during service. Fitment examples include Fits 1970 Chevrolet Corvette, N/A; Fits 1965-1968 Chevrolet Corvette, N/A; Fits 1966 Chevrolet El Camino, N/A; and Fits 1962 Pontiac Laurentian, N/A.

Quality Assurance

Autolite supplies ignition products to the automotive aftermarket and original equipment manufacturers, with OE-style form, fit, and function as a core product standard. The 403 spark plug is built to match common service requirements for older Honda, Volkswagen, Porsche, Chevrolet, and Pontiac applications.