NGK 6684 Spark Plug

NGK Iridium IX Spark Plug 6684

NGK Iridium IX Spark Plug 6684 is built for precise ignition performance in select Porsche 911 and Maserati applications. It combines an iridium center electrode with a nickel ground electrode and a 0.032 in pre-gap for consistent spark delivery and stable combustion.

Key Features

• Iridium center electrode tip for focused spark performance
• Copper center electrode core for efficient heat transfer
• Nickel ground electrode core with taper cut tip design
• Standard ground configuration with one ground electrode
• 5000 ohm resistance for ignition system compatibility
• Flat seat, 14 mm thread diameter, 0.75 in reach, and 13/16 in hex size
• Manufacturer heat range 8

Iridium IX Product Line Details

NGK Iridium IX spark plugs are part of NGK’s performance-focused ignition line, using an iridium firing tip to support reliable spark concentration and long service life in demanding street applications. Part number 6684 is listed as BPR8EIX and is engineered to meet the needs of specific Porsche 911 and Maserati engines that require this plug specification.

Detailed Description

NGK 6684 is a direct-fit spark plug for select 1970-1990 Porsche 911 models and 1983-1990 Maserati Biturbo and 430i applications. The plug’s iridium tip, copper core, and taper cut ground electrode are specified to support consistent ignition under the operating conditions these engines require. This part cross-references AMS Automotive 6684 for the same application.

Common Issues This Spark Plug Can Address

• Hard starting caused by worn or fouled spark plugs
• Rough idle from inconsistent ignition output
• Misfire conditions related to degraded plug electrodes
• Reduced throttle response from weak spark delivery
• Maintenance replacement for service intervals on Porsche 911 and Maserati ignition systems

Installation Notes and Tips

Verify the specified gap before installation and set it to the vehicle requirement listed in the fitment notes: 0.024 in for many Porsche 911 applications and 0.028 in for the Maserati applications shown. Confirm the flat seat design, 14 mm thread diameter, 0.75 in reach, and 13/16 in hex size match the cylinder head specification before tightening. Use the removable nut terminal only where the ignition lead or coil connection calls for it.

Quality Assurance

NGK is a long-established OE supplier and manufacturer with broad coverage across automotive, motorcycle, marine, and small engine ignition applications. Part number 6684 reflects NGK’s focus on original-equipment-level manufacturing standards and application-specific fitment for select Porsche 911 and Maserati engines.

Compatible With Select Vehicles

• Fits 1989-1990 Maserati 430i, N/A; set spark plug gap to 0.028 inches.
• Fits 1983-1987 Maserati Biturbo, N/A; set spark plug gap to 0.028 inches.
• Fits 1981-1989 Porsche 911, N/A; spark plug gap: 0.024 inches.
• Fits 1976-1977 Porsche 911, N/A; spark plug gap: 0.024 inches.
• Fits 1974-1975 Porsche 911, N/A; set spark plug gap to 0.028 inches.
• Fits 1970-1973 Porsche 911, N/A; spark plug gap: 0.024 inches.