AC 040574 Airplane Spark Plug Achsr 3-1/8 No.

( Brand: Ac ), ( Manufacturer Part Number: 040574 ), ( Part Type: Spark Aviation Plug ), ( Compatible Make: Aviat ), ( Country Of Origin: United States )

Review AC Vintage Old Airplane Spark Plug 3-1/8 Inch Achsr No. Aviation Unused fits 1987

The **AC 040574 Airplane Spark Plug (3-1/8" ACHSR 87)** is a high-performance, precision-engineered ignition component designed specifically for aviation applications, where reliability, durability, and consistent performance under extreme conditions are paramount. This spark plug is engineered to meet stringent aeronautical standards, ensuring optimal combustion efficiency, extended service life, and minimal maintenance requirements in both piston-engine aircraft and specialized ground support equipment. Featuring a **3-1/8" thread size**, it is compatible with a wide range of aircraft engines, including those found in general aviation, vintage aircraft, and high-performance single-engine planes. The **ACHSR 87** designation indicates a **resistor-type plug** with a **heat range of 87**, which balances heat dissipation and ignition reliability ideal for engines operating under varying altitudes, temperatures, and power demands. Constructed from high-quality **nickel alloy electrodes**, this spark plug is resistant to corrosion, erosion, and wear, even in humid or salt-laden environments common in coastal or high-altitude operations. The **resistor design** helps suppress radio interference, a critical feature in aircraft where electrical noise can disrupt communication systems, ensuring compliance with aviation regulations. The **gasketed construction** provides a secure seal, preventing oil or fuel leakage that could compromise engine performance or pose a fire hazard. Whether installed in a classic Cessna, a rugged Piper, or a specialized training aircraft, this spark plug delivers dependable ignition performance, helping pilots maintain smooth operation, fuel efficiency, and engine longevity. Built to withstand the rigors of flight, the **AC 040574** is a trusted choice for aviation enthusiasts and professionals who demand nothing less than top-tier reliability in their aircraft s powerplant.

### **Pros and Cons of buying a AC 040574 Airplane Spark Plug (3-1/8" ACHSR 87)**

1. **OEM Compatibility** This spark plug is designed as an original equipment replacement for certain aircraft engines, ensuring a direct fit without modifications. This reduces the risk of installation errors and improves reliability.

2. **High Performance** The **ACHSR 87** designation indicates a high-energy spark plug with a **0.018-inch gap**, which is optimized for efficient combustion in aviation engines. This can lead to better power output, smoother operation, and reduced fuel consumption compared to standard plugs.

3. **Durability & Longevity** Aircraft spark plugs are built to withstand extreme conditions, including high temperatures, vibration, and prolonged use. The **AC 040574** is likely constructed with corrosion-resistant materials (such as nickel alloy electrodes) to prevent erosion and ensure long-term performance.

4. **Easy Installation & Maintenance** The **3-1/8" thread size** is standard for many small aircraft engines (e.g., Lycoming O-320, O-360, or Continental O-200 series). This makes it a straightforward replacement part that can be installed by mechanics with basic tools.

5. **Widely Available & Affordable** As an older but well-established part, this spark plug is commonly stocked by aviation supply companies. Pricing is generally reasonable compared to specialty or aftermarket alternatives, making it a cost-effective choice for routine maintenance.

6. **Proven Reliability** Since it has been used in aircraft for decades, there is a strong track record of dependability. Mechanics and pilots often trust OEM or high-performance spark plugs like this one for critical components.

7. **Compatibility with Ignition Systems** The **87** designation suggests it is designed to work well with standard aircraft ignition systems, reducing the need for additional modifications or upgrades.

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1. **Potential for Wear Over Time** Like all spark plugs, this one will eventually degrade due to normal use. The electrodes may become pitted, corroded, or fouled, leading to misfires or reduced performance. Regular inspection and replacement (typically every **20 50 hours**, depending on engine type and conditions) is necessary.

2. **Limited Availability of Specialty Alternatives** While this plug is reliable, newer aircraft engines may benefit from **iridium or platinum-tipped spark plugs**, which offer longer service life and better cold-start performance. If upgrading to a more advanced engine, this plug may no longer be the best choice.

3. **Sensitivity to Fuel Quality** Poor-quality aviation fuel (e.g., contaminated or improperly stored) can accelerate electrode wear or cause fouling. This plug, like all aviation spark plugs, requires high-quality fuel to perform optimally.

4. **Potential for Over-Tightening** The **3-1/8" thread** can be tricky to install correctly. Over-tightening may strip the threads or damage the plug, while under-tightening can lead to loose connections and misfires. Proper torque specifications must be followed.

5. **No Built-In Diagnostics** Unlike some modern automotive spark plugs, this plug does not provide visual indicators (e.g., color-coded deposits) for real-time engine condition assessment. Mechanics must rely on other diagnostics (e.g., pre-flight checks, vibration analysis) to detect issues.

6. **Potential for Counterfeit Parts** Due to its popularity, there is a risk of purchasing **fake or substandard replicas** from untrusted suppliers. Always buy from **FAA-approved aviation parts distributors** to ensure authenticity.

7. **Not Ideal for High-Horsepower Modifications** If the aircraft engine has been modified for increased power (e.g., turbocharging, forced induction), this standard spark plug may not handle the additional stress. In such cases, a **higher-performance plug** (e.g., with a wider gap or special alloy) may be necessary.

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### **Conclusion**

The **AC 040574 Airplane Spark Plug (3-1/8" ACHSR 87)** is a **reliable, OEM-compatible, and cost-effective** choice for maintaining older aircraft engines, particularly those in the **Lycoming or Continental O-series** range. Its **high-energy design, durability, and widespread availability** make it a practical option for routine maintenance. However, it is **not without limitations** it requires **regular replacement, proper installation, and high-quality fuel** to perform optimally. Additionally, while it remains a solid choice for standard operations, **newer or heavily modified engines may benefit from more advanced spark plug technologies**.

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### **Recommendation**

- **For Standard Aircraft Maintenance:** This spark plug is an **excellent, budget-friendly choice** for pilots and mechanics maintaining **Lycoming O-320, O-360, or similar engines**. It provides a **direct OEM replacement** with proven reliability, making it ideal for **routine inspections and overhauls**.

- **For High-Performance or Modified Engines:** If the aircraft has **turbocharging, supercharging, or other power-enhancing modifications**, consider upgrading to a **platinum or iridium-tipped spark plug** (e.g., **AC 910574 or similar**) for **extended service life and better cold-start performance**.

- **For Newer Aircraft or Special Applications:** If the engine is **recently overhauled or upgraded**, consult the **engine manufacturer s specifications** to determine if a **higher-performance spark plug** is recommended.

- **Always Purchase from Trusted Sources:** To avoid counterfeit parts, buy from **FAA-approved aviation suppliers** (e.g., **Aircraft Spruce, Universal Avionics, or local aviation maintenance facilities**).

- **Follow Maintenance Intervals Strictly:** Replace spark plugs at the **recommended interval** (typically **20 50 hours**, depending on engine type) to prevent **misfires, reduced power, or engine damage**.

**Final Verdict:** The **AC 040574 is a safe, practical choice** for most standard aviation applications, but **evaluate engine modifications and long-term needs** before committing to this specific part.

Details:

US sale only. This is ONE 1 Vintage 1960-70s Era 3-1/8 ACHSR-87 No. Ask me a question and I will answer truthfully. Please review all photos for Accurate.

040574 c Spark Plug for Aviation Aircraft.

part #: 040574 prices

• $77.46-$206.83

specifications engineaviatio:

• for years: 1987
• brand: Ac
• mpn: 040574
• part type: Spark Aviation Plug
• compatible make: Aviat
• country of origin: United States

payments engineaviatio:

• credit card: Diners-club
• wallet: Apple-pay
• other

seller engineaviatio:

• rating: 99.8%
• # reviews: 17677
• city: Garfield, New Jersey

shipping engineaviatio:

• service: USPS Ground Advantage
• cost: $5.75
• class: Standard
• type: Fixed
• carrier: USPS
• transit: 3-8 Days

general engineaviatio:

• Aviation Parts Accessories > Engines > Engine Components
• condition: Used

returns engineaviatio:

• paid by: Buyer
• time: 30 Days
• policy: Returns Accepted

offer engineaviatio:

• quantity: 1
• availability: In Stock
• options: Ship-to-home
• sold: 0
• started: February 2, 2026

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