Autolite 847 Spark Plug

Autolite 847 Copper Resistor Spark Plug

Autolite 847 is an OE-style copper resistor spark plug built for quick starts, smooth acceleration, and consistent ignition performance. It is a practical replacement choice for older Buick, Oldsmobile, Pontiac, and Cadillac applications that call for a copper-core plug with a resistor design.

The Copper Resistor Spark Plug line focuses on OE form, fit, and function for a wide range of domestic and foreign vehicles. For drivers servicing classic GM applications, Autolite 847 provides the core specifications needed for proper ignition system operation, including a 14 mm thread, flat seat, 0.374-inch reach, and 0.070-inch pre-gap.

Key Features

• Copper center electrode core for reliable ignition response
• 5000 ohm resistor design to help control electrical noise
• Nickel center and ground electrode tip materials
• Tapered ground electrode tip design with one ground electrode
• Ceramic insulator with mid-projection design
• 14.0 mm thread diameter, 13/16 in. hex, flat seat
• Pre-gapped at 0.070 in. / 1.80 mm

Product Details

Autolite 847 is engineered as a direct OE-style spark plug for ignition service on older GM platforms, including Buick LeSabre, Oldsmobile Cutlass, and Pontiac Firebird applications listed in the fitment data. The copper core supports dependable spark delivery, while the resistor construction helps maintain stable ignition performance in resistor-equipped systems. This part number is also referenced as Autolite 66 for cross-reference purposes.

This part cross-references AR82-6 and R46SZ for the same application.

What It Helps Address

• Hard starting caused by worn or fouled spark plugs
• Rough idle from inconsistent spark delivery
• Misfire concerns related to aged ignition components
• Reduced throttle response in older ignition systems
• Electrical interference in resistor plug applications

Installation Notes

Verify the required gap and heat range against the vehicle service specification before installation. Autolite 847 is a flat-seat plug with a 14 mm thread, 13/16 in. hex, and 0.374-inch reach, so confirm cylinder head compatibility before threading in the plug. For fitment-specific applications such as 1973-1974 Oldsmobile models with HEI and 1976 late/except-late configurations, match the notes in the vehicle listing exactly.

Compatible With 1973-1985 Buick, Cadillac, Oldsmobile, and Pontiac applications listed in the fitment data, including Buick LeSabre, Oldsmobile Cutlass, and Pontiac Firebird. Fits 1973-1974 Oldsmobile 98, 1976 Oldsmobile Cutlass, and 1980-1984 Buick Riviera applications as specified.

Quality Assurance

Autolite supplies ignition products to the automotive aftermarket and original equipment manufacturers, with a focus on OE-style fit and function. Part number 847 is built to the listed specifications for service on the confirmed vehicle applications.