NGK R0373A-10 Spark Plug Sparkplug Racing No. 4940

( Brand: Ngk ), ( Manufacturer Part Number: R0373A-10 ), ( Type: Spark Plug ), ( Reference Oe/oem Number: 09482-00430, G 56 R, Iu 01-31, 90793-20149, 94700-00394 ), ( Country Of Origin: Japan )

Review NGK Spark Plug Sparkplug Type Racing R0373a10 No.

The **NGK R0373A-10** is a high-performance spark plug designed specifically for racing applications, engineered to deliver exceptional reliability, precision ignition, and superior combustion efficiency in demanding engine environments. Part of NGK s **Laser Iridium** line, this plug features a **0.7mm iridium center electrode** paired with a **copper-nickel alloy ground electrode**, creating an ultra-fine gap that ensures optimal spark consistency even under extreme conditions. The **resistorless design** eliminates radio interference, making it ideal for high-revving engines where clean ignition performance is critical. With a **thread size of 14mm (M14 x 1.25)** and a **reach of 19mm**, it is meticulously crafted for precise installation in modern racing engines, including those in **NASCAR, NHRA, and drag racing applications**, where durability and performance are non-negotiable.

The **Laser Iridium tip** provides a longer lifespan compared to traditional platinum or copper plugs, reducing maintenance downtime and ensuring consistent spark delivery across high-stress operating cycles. Its **heat range of 4940** (classified as a **cold plug**) makes it suitable for high-compression, forced-induction, or turbocharged engines, where heat dissipation is critical to prevent pre-ignition and knock. The **copper-nickel ground electrode** enhances heat transfer, reducing fouling and improving combustion stability, while the **ceramic insulator** is reinforced for thermal shock resistance, ensuring longevity even under extreme temperature fluctuations. Whether used in **high-revving V8s, turbocharged inline-6s, or supercharged engines**, the R0373A-10 delivers the precision and power required to maximize horsepower and torque while maintaining reliability.

Built to withstand the rigors of competitive racing, this spark plug is a favorite among engine builders and tuners who demand the best in ignition performance. Its **non-resistor design** ensures a strong, clean spark with minimal voltage drop, making it perfect for high-output applications where every spark counts. The **tight electrode gap** promotes efficient combustion, reducing fuel waste and improving throttle response, while its **robust construction** ensures it can handle the demands of repeated high-load cycles without degradation. For racers and performance enthusiasts seeking a spark plug that bridges the gap between durability and high-performance ignition, the **NGK R0373A-10** stands as a proven choice delivering the precision, power, and reliability needed to dominate on the track.

### **Pros and Cons of buying a NGK R0373A-10 (4940) Spark Plug**

1. **High-Performance Design** The R0373A-10 is a racing-grade spark plug with a fine-wire electrode (0.6 mm) and a copper core, which promotes faster ignition and better combustion efficiency. This makes it ideal for high-performance engines, including turbocharged or supercharged applications.

2. **Durability and Heat Resistance** The plug is made with a nickel alloy electrode and a ceramic insulator, which enhances resistance to heat and wear. This extends its lifespan compared to standard plugs, especially in demanding conditions.

3. **Improved Engine Response** The fine wire and optimized gap (0.7 0.8 mm) help achieve a more consistent spark, leading to smoother power delivery, better throttle response, and reduced misfires in high-RPM applications.

4. **Compatibility with Aftermarket Modifications** Since this is a racing plug, it works well with forced induction (turbo/supercharger) setups, high-compression engines, and performance chips. It can help mitigate detonation risks in modified engines.

5. **NGK s Reputation for Reliability** NGK is a well-known brand with a strong track record in manufacturing high-quality spark plugs, ensuring consistent performance and durability.

6. **Better Fuel Efficiency (in Some Cases)** A properly functioning spark plug can improve combustion efficiency, potentially leading to slight gains in fuel economy, though this is more noticeable in high-performance applications.

7. **Easier Break-In for New Engines** The fine wire and copper core can help new engines achieve smoother break-in periods by promoting more stable ignition.

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1. **Not Suitable for Stock or Mildly Modified Engines** This is a **racing plug**, meaning it is **not recommended** for daily driving in stock or lightly modified engines. It may cause pre-ignition (knocking) in normally aspirated engines due to its heat range and fine wire.

2. **Shorter Lifespan Compared to Standard Plugs** Racing plugs generally wear out faster than stock plugs (typically 10,000 20,000 miles vs. 30,000 100,000 miles for standard plugs). This means more frequent replacements, which can be costly over time.

3. **Higher Cost** NGK s racing plugs are significantly more expensive than standard plugs. For example, the R0373A-10 costs more than a typical iridium or platinum plug, making it a less economical choice for daily use.

4. **Potential for Pre-Ignition (Knocking)** If installed in an engine not designed for high-performance plugs, the R0373A-10 may cause **detonation (knocking)**, leading to engine damage if not addressed immediately. This is a serious risk in stock or improperly tuned engines.

5. **Requires Proper Gap Setting** The plug s fine wire and specific gap (0.7 0.8 mm) must be set correctly. Incorrect gapping can lead to misfires, poor performance, or even failure.

6. **Limited Availability in Some Regions** Racing plugs like this may not be as widely stocked as standard plugs, requiring special ordering in some cases.

7. **Not Ideal for Cold Weather or Wet Conditions** The fine wire and lower heat range can make it more prone to fouling in cold or humid environments compared to colder-range plugs.

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The **NGK R0373A-10** is an excellent choice for **high-performance, forced-induction, or racing applications** where maximum power, reliability, and ignition speed are critical. Its fine wire and racing-grade construction make it superior for engines running at high RPMs, under boost, or with aggressive tuning. However, it is **not suitable for stock or mildly modified engines**, as it can cause knocking and potential engine damage.

If you are running a **turbocharged, supercharged, or high-performance naturally aspirated engine with proper tuning and cooling**, this plug will significantly enhance performance. For **daily driving or stock engines**, a standard iridium or platinum plug (e.g., NGK Iridium IX or Denso NK36HR11) would be a safer and more cost-effective choice.

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- You are running a **high-performance, turbocharged, or supercharged engine**.

- Your engine has **proper cooling and tuning** to prevent pre-ignition.

- You are prepared for **more frequent replacements** due to its shorter lifespan.

- You need **maximum ignition reliability and power output** in a racing or modified setup.

- You are using a **stock or mildly modified engine** without forced induction.

- Your engine lacks **proper cooling or detonation protection** (e.g., no octane boost or cooling mods).

- You prioritize **longer plug life and lower cost** over performance gains.

- You drive in **cold or wet conditions** frequently, as it may foul more easily.

For most **daily drivers**, a **high-quality standard plug (e.g., NGK Iridium IX or Denso NK36HR11)** is a better balance of performance, reliability, and cost. The R0373A-10 is best reserved for **serious performance builds where maximum ignition efficiency is non-negotiable**.

Details:

4pcs in each box Price is per. Ngk racing spark plugs. Applications or any extreme application. I'm selling 2 boxes.

The SE are the highest quality spark plugs you can get. These are ideal for high comp.

part #: r0373a10 prices

• $42.03-$150.00

specifications cyclesparkplugs:

• brand: Ngk
• mpn: R0373a-10
• type: Spark Plug
• reference oe/oem number: 09482-00430, G 56 R, Iu 01-31, 90793-20149, 94700-00394
• country of origin: Japan

general cyclesparkplugs:

• condition: New
• Motorcycle Scooter Parts Accessories > Electrical Ignition Components > Spark Plugs

payments cyclesparkplugs:

• other
• wallet: Google-pay
• credit card: Discover

shipping cyclesparkplugs:

• carrier: UPS
• type: Calculated
• class: Standard
• service: UPS Ground
• cost: $0.00
• transit: 4-11 Days

offer cyclesparkplugs:

• quantity: 2
• availability: In Stock
• options: Ship-to-home
• best offers: True
• started: May 17, 2026
• sold: 0

returns cyclesparkplugs:

• policy: No Returns

seller cyclesparkplugs:

• rating: 100.0%
• city: Fort Myers, Florida
• # reviews: 127

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