NGK 4656 R7438-9 Iridium Racing Spark Plug Extra Cold for High HP Race Engines

Vehicle Fitment

• Universal - Fits high-performance automotive, motorcycle, and marine race engines with 14mm x 1.25mm thread (M14)

Fitment Notes

• This is a universal racing spark plug - no specific vehicle application is assigned by NGK
• Intended for modified, high-compression, or forced-induction race engines only
• Gap adjustment required; preset gap of 0.028" (0.7mm) is a general starting point
• Not recommended for stock or lightly modified street engines

Features

• Fine wire iridium-tipped center electrode for enhanced ignitability and durability
• Platinum-tipped ground electrode for improved spark consistency and longevity
• Extra-cold heat range (9) designed for high-horsepower and high-compression applications
• Pure alumina silicate ceramic insulator for superior strength and heat transfer
• Corrugated ribs on insulator prevent flashover under high-voltage conditions
• Copper core aids in heat removal and supports ultra-wide heat range performance
• Triple seals prevent combustion leakage and protect internal components
• 5,000 Ohm resistor suppresses electrical interference for cleaner ignition signal

Specifications

• Part Number: 4656 / R7438-9
• Thread Diameter: 14mm
• Thread Pitch: 1.25mm
• Thread Reach: 26.5mm (1.04")
• Hex Size: 5/8" (16mm)
• Seat Type: Gasket (Flat)
• Heat Range: 9 (Extra Cold)
• Preset Gap: 0.028" (0.7mm)
• Center Electrode: Fine Wire Iridium, 1.0mm, Non-Projected
• Ground Electrode: Platinum-Tipped, Slant Configuration
• Center Electrode Core: Copper
• Resistor: Yes - 5,000 Ohm
• Terminal Type: Solid (Non-Removable Nut)
• Insulator Height: 50mm (1.990")
• Torque - Cast Iron: 18-25.3 lb-ft | Aluminum: 18-21.6 lb-ft

Included Components

• 1x NGK 4656 (R7438-9) Racing Spark Plug

Product Description

The NGK 4656 (R7438-9) is a purpose-built racing spark plug engineered for high-horsepower, high-compression, and forced-induction race engines. Featuring a fine wire iridium center electrode paired with a platinum-tipped slant ground electrode, this plug delivers reliable ignition under the extreme thermal and mechanical stress of race conditions. The extra-cold heat range (9) makes it ideal for engines running aggressive timing, high-octane fuel, or forced induction where heat control is critical.

Built with NGK's alumina silicate ceramic insulator and copper core, the R7438-9 efficiently transfers heat away from the combustion chamber while maintaining dielectric integrity. The corrugated insulator ribs prevent flashover, and triple seals block any combustion leakage. This plug is sold individually, making it easy to purchase the exact quantity needed for your specific engine configuration - whether 4-cylinder, 6-cylinder, or beyond.