Autolite 685 Spark Plug

Autolite Copper Resistor Spark Plug 685

Autolite 685 is a copper resistor spark plug built for OE-style ignition performance, quick starts, smooth acceleration, and consistent fuel economy. With a 0.060 in. pre-gap, 5,000 ohm resistance, and tapered seat design, it serves as a direct-style replacement for a wide range of classic Chevrolet and GMC applications.

The Autolite Copper Resistor Spark Plug line focuses on OE form, fit, and function for domestic and foreign vehicles. This makes the 685 a practical choice for drivers restoring or maintaining older ignition systems that call for a copper-core plug with a standard resistor design.

Key Features

• Copper center electrode core for reliable ignition performance
• 5,000 ohm resistor design to help control electrical noise
• 0.060 in. pre-gap for listed applications
• Tapered seat and 14 mm thread diameter
• Nickel center and ground electrode tip materials
• Ceramic insulator with short insulator type
• 5/8 in. hex size for standard service tools

Detailed Description

Autolite 685 is engineered as a copper resistor spark plug for OE-style service in ignition systems that specify this configuration. The standard copper core supports dependable spark delivery, while the nickel tip materials and tapered ground electrode design help maintain stable operation in everyday driving. This part number is commonly selected for classic Chevrolet and GMC trucks, vans, and passenger cars that require the listed gap and tapered-seat plug design.

Fits 1975 Chevrolet C10, N/A; Fits 1975 Chevrolet C10 Suburban, N/A; Fits 1975 Chevrolet C20, N/A; Fits 1975 Chevrolet C20 Suburban, N/A; Fits 1975 Chevrolet C30, N/A; Fits 1975 Chevrolet Camaro, N/A; Fits 1975 Chevrolet Caprice, N/A; Fits 1975 Chevrolet Corvette, N/A; Fits 1975 Chevrolet El Camino, N/A; Fits 1975 Chevrolet G20, N/A; Fits 1975 Chevrolet G30, N/A; Fits 1975 Chevrolet Impala, N/A; Fits 1975 Chevrolet K10, N/A; Fits 1975 Chevrolet K10 Suburban, N/A; Fits 1975 Chevrolet K20, N/A; Fits 1975 Chevrolet K20 Suburban, N/A; Fits 1975 Chevrolet K5 Blazer, N/A; Fits 1975 Chevrolet Malibu, N/A; Fits 1975 Chevrolet Monte Carlo, N/A; Fits 1975 Chevrolet Monza, N/A; Fits 1975 Chevrolet Nova, N/A; Fits 1975 Chevrolet P10, N/A; Fits 1975 Chevrolet P20, N/A; Fits 1975 Chevrolet P30, N/A; Fits 1975 GMC G25, N/A; Fits 1975 GMC G35, N/A; Fits 1977-1978 Chevrolet El Camino, N/A; Fits 1977-1978 Chevrolet G10, N/A; Fits 1977-1978 Chevrolet G20, N/A; Fits 1977-1978 Chevrolet G30, N/A; Fits 1977-1978 Chevrolet P10, N/A; Fits 1977-1978 Chevrolet P20, N/A; Fits 1976-1978 Chevrolet P30, N/A; Fits 1977-1978 GMC G15, N/A; Fits 1977-1978 GMC G25, N/A; Fits 1977-1978 GMC G35, N/A; Fits 1977-1978 GMC Jimmy, N/A.

This part cross-references DENSO Auto Parts 5030 and Gates 7240 for the same application.

Common Uses

• Hard starting caused by worn or incorrect spark plugs
• Rough idle in older carbureted ignition systems
• Misfire concerns tied to plug wear or incorrect gap
• Reduced throttle response during acceleration
• Routine tune-up service on classic Chevrolet and GMC vehicles

Installation Notes and Tips

Verify the required thread diameter, reach, seat type, and gap before installation. Autolite 685 uses a 0.060 in. pre-gap and a tapered seat, so it should be matched to the engine specification listed for the vehicle. Check plug wire condition, ignition timing, and distributor components during service to help maintain consistent ignition performance.

Quality Assurance

Autolite supplies ignition products to the automotive aftermarket and original equipment manufacturers, and this spark plug is built to OE-style form, fit, and function standards for the listed applications.