Autolite 646 Spark Plug

Reliable Ignition Performance for Select Domestic Vehicles

The Autolite Copper Resistor Spark Plug 646 is engineered to deliver consistent ignition performance for a range of domestic vehicles including Buick, Cadillac, Chrysler, Dodge, Oldsmobile, Plymouth, and Pontiac models. Designed with durable materials and precise specifications, this spark plug supports efficient combustion and engine reliability.

• Part Number: 646
• Brand Line: Copper Resistor Spark Plug
• Ground Electrode Tip Design: Tapered nickel
• Center Electrode Core Material: Copper with nickel tip
• Electrical Terminal Type: Stud
• Pre-Gap Size: 0.050 inches (1.30 mm)
• Hex Size: 13/16 inch (21 mm)
• Thread Diameter: 14.0 mm with 0.750 inch (19.5 mm) reach
• Seat Type: Flat
• Insulator Material: Ceramic with mid projection design
• Resistor Type: Yes, reduces electrical noise interference

About the Autolite Copper Resistor Spark Plug Line

The Copper Resistor Spark Plug line from Autolite is designed to provide reliable ignition with enhanced electrical noise suppression. Featuring a copper core center electrode for improved conductivity and a resistor to minimize radio frequency interference, these spark plugs are suitable for a variety of domestic vehicles. The tapered nickel ground electrode tip and ceramic insulator ensure durability and consistent spark delivery under normal operating conditions.

Technical Description and Benefits

This spark plug incorporates a copper core center electrode with a nickel tip, which promotes efficient heat transfer and stable spark generation. The tapered ground electrode tip made of nickel enhances spark exposure and combustion efficiency. The flat seat and 14.0 mm thread diameter with a 0.750 inch reach ensure proper fitment in compatible engines. The mid projection ceramic insulator provides electrical insulation and heat resistance, while the resistor helps reduce electromagnetic interference that can affect vehicle electronics.

Compatible Vehicles and Applications

• Buick models including LeMans and Skylark
• Cadillac DeVille, Eldorado, and Seville
• Chrysler Concorde and Intrepid
• Dodge Caravan, Grand Caravan, and Town & Country
• Oldsmobile Firenza and Cutlass
• Plymouth Voyager and Grand Voyager
• Pontiac Dynasty and Sunbird

Common Issues Addressed by This Spark Plug

• Engine misfires due to worn or faulty spark plugs
• Reduced fuel efficiency from incomplete combustion
• Difficulty starting the engine in cold conditions
• Electrical interference affecting vehicle electronics
• Rough idling or hesitation during acceleration

Installation Notes and Tips

Ensure the spark plug gap is set to the specified pre-gap size of 0.050 inches (1.30 mm) before installation. Use a torque wrench to tighten the spark plug to the manufacturer’s recommended torque specification to avoid damage to the threads or seat. The 13/16 inch (21 mm) hex size allows for standard spark plug socket compatibility. Inspect the spark plug hole for debris before installation to ensure proper seating and sealing.

Quality Assurance and Warranty

Autolite spark plugs are manufactured to meet OEM specifications for fit, form, and function. The Copper Resistor Spark Plug 646 undergoes rigorous quality control to ensure consistent performance and durability. While specific warranty details may vary, Autolite products typically come with a limited warranty against manufacturing defects. Consult product documentation or the vehicle manufacturer for warranty coverage details.