NGK Racing Spark Plug – NGK-R7438-9 (4656)
The NGK R7438-9 is a purpose-built racing spark plug designed for highly tuned engines operating under extreme conditions. As an authorised NGK retailer, we supply these genuine racing-grade plugs to drivers who demand consistent ignition performance when their engine is pushed well beyond standard parameters.
This plug is recommended for bespoke track vehicles or customers running high-powered Stage 3 (or beyond) setups with an enthusiastic driving style. Switching to a colder, race-specification plug helps prevent misfires that can occur when aggressive tuning and high cylinder pressures begin to overwhelm standard road plugs.
Sold individually. Please add the correct number of plugs for your engine to your cart (typically one per cylinder).
Gapping and Setup
These plugs arrive pre-gapped from the factory and must not be adjusted. The fine-wire iridium ground electrode is extremely delicate, and attempting to gap it manually will almost certainly damage the plug. Fit them as supplied.
Why Choose a Racing Spark Plug?
Standard spark plugs are designed for a balance of longevity and everyday driveability. Once an engine is tuned to higher boost pressures, leaner fuel mixtures or higher RPM, the in-cylinder environment becomes far more demanding. A racing plug like the R7438-9 runs cooler (a “colder” heat range), shedding combustion heat more quickly to prevent pre-ignition and detonation, two issues that can rapidly destroy a tuned engine.
The trade-off is that race plugs are not ideal for low-load city driving, where they can be prone to fouling. They are best suited to vehicles that see regular spirited use, track work or competition.
Key Features
- Fine-wire iridium centre electrode for a stable, consistent spark and excellent durability
- Iridium alloy tip with a very high melting point, ideal for high-output modern engines
- Trivalent metal plating provides anti-corrosion and anti-seize properties
- Corrugated ribs on the insulator help prevent flashover (spark tracking down the outside of the plug)
- Pure alumina silicate ceramic insulator for strength and improved heat transfer
- Solid copper core helps remove heat efficiently from the firing tip
- Triple seals prevent combustion gas leakage
Technical Information
| Part Number | NGK-R7438-9 (Stock No. 4656) |
| Type | Resistor, Racing |
| Pre-set Gap | 0.9mm (0.04″) |
| Insulation Projection | 0.9mm (0.04″) |
| Electrode Material | Iridium fine wire |
To confirm this plug is suitable for your vehicle and tuning stage, please use the vehicle lookup on our site or check the Vehicle Fitment tab for full compatibility details.
About NGK
NGK is the brand leader in the UK spark plug market and one of the largest OE suppliers to major vehicle manufacturers worldwide. Their plugs are trusted by teams competing in F1, WRC and MotoGP, and the same engineering principles flow down into their road and racing product ranges.
With over 1,000 different spark plug types in production, NGK invests heavily in research and development to keep pace with modern engine technology. The result is a genuine, race-proven product that sits at the heart of countless smooth-running engines around the world.
Applications
Please note, customers are wholly responsible for checking fitment for their vehicle.



