JACOBS RADIAL ENGINE 711-B Aircraft Piston Top R-915 L6MB R52 2.90

( Brand: Jacobs Radial Engine ), ( Manufacturer Part Number: 711-B ), ( Part Type: Piston ), ( Compatible Make: R-915 / L6mb )

Review JACOBS RADIAL ENGINE Aircraft Piston Engraved On Top 711b R52 2.90

The **Jacobs R-915 L6MB (Model 711-B) aircraft radial engine** stands as a legendary powerplant in aviation history, renowned for its robust performance, reliability, and distinctive six-cylinder radial design. Originally developed by the Jacobs Aircraft Engine Company in the 1930s, this engine specifically the **R-915 variant** was a refined iteration of the company s earlier radial engines, tailored for general aviation, military liaison, and training aircraft. The **711-B** designation refers to a later model iteration, incorporating improvements in cooling efficiency, fuel economy, and durability while maintaining the signature radial configuration that made Jacobs engines so beloved by pilots. With a displacement of **2.90 liters (177 cubic inches)**, the R-915 L6MB delivers a balanced blend of power and efficiency, producing approximately **145 horsepower at takeoff** (though variations exist depending on modifications and altitude adjustments) while operating at a modest **2,200 RPM** under standard conditions. Its **air-cooled, horizontally opposed cylinders** arranged in a single row around a central crankshaft provide exceptional cooling performance, reducing the risk of overheating even during prolonged operations at lower altitudes.

One of the defining features of the R-915 L6MB is its **supercharged or naturally aspirated flexibility**, depending on the application. Many versions of this engine were equipped with a **gear-driven supercharger**, allowing it to maintain near-ground-level performance at higher altitudes a critical advantage for military and utility aircraft of the era. The **R-52** designation (sometimes seen in conjunction with the 711-B) may refer to a specific model variant or a production run with particular refinements, such as revised cylinder heads, improved valve timing, or enhanced ignition systems. The engine s **piston-top design** (often referred to as the "Jacobs piston crown" or "dish-shaped" pistons) was a hallmark of its efficiency, reducing heat transfer to the cylinder walls while optimizing combustion. This design, combined with **dry-sump lubrication** (in many later models), ensured longevity and reduced maintenance demands, making it a favorite among pilots who valued both performance and ease of upkeep.

The **711-B R-915 L6MB** was widely adopted in a variety of aircraft, including the **Stinson L-5 Sentinel** (a World War II-era liaison and observation plane), the **Beechcraft Model 17 Staggerwing**, and other light utility and training aircraft. Its compact size, lightweight construction (weighing around **350 400 pounds dry**), and relatively low fuel consumption made it an ideal choice for short-haul operations, aerial photography, and even some experimental designs. The engine s **direct-drive configuration** (without a reduction gear in many cases) allowed for straightforward installation, though some later models incorporated a **reduction gearbox** to optimize propeller speed. Maintenance was simplified by the engine s **easy access to critical components**, such as the **magneto system, carburetor, and valve mechanism**, all of which were designed for quick inspection and adjustment an essential feature for pilots operating in remote or austere conditions.

Beyond its technical specifications, the **Jacobs R-915 L6MB** holds a nostalgic place in aviation history as a symbol of mid-20th-century engineering ingenuity. Its radial design, while less common in modern aviation, offered unmatched reliability in an era before electronic fuel injection and complex turbocharging systems. The engine s **timeless simplicity**, combined with its ability to thrive in demanding environments, has ensured its legacy among aviation enthusiasts and restorers. Today, the **711-B R-915** remains a sought-after powerplant for vintage aircraft restoration projects, offering a blend of historical charm and practical performance that continues to captivate pilots and engineers alike. Whether in a restored World War II-era liaison plane or a modern retrofitted light aircraft, this engine embodies the spirit of early aviation where power, durability, and pilot-friendly design were paramount.

### **Pros and Cons of Buying a Jacobs R-915 L6MB (711-B) Aircraft Engine**

The **Jacobs R-915 L6MB (711-B)** is a six-cylinder, air-cooled radial piston engine originally developed for military use but widely adopted in general aviation. Below is a detailed analysis of its advantages and disadvantages, followed by a concluding recommendation.

---

### **Pros**

1. **Reliability and Durability**

- The R-915 is known for its robust construction, with many engines accumulating **10,000 hours** with proper maintenance. It was designed for rugged conditions, making it suitable for bush, military, and utility operations.

- The engine s **simple, proven design** (similar to Lycoming and Continental radials) means it is easier to repair than some modern turbocharged or fuel-injected engines.

2. **Fuel Flexibility**

- The R-915 can operate on **80/87 octane aviation gasoline (AVGAS)** as well as **100LL**, though performance is optimized with higher-octane fuel.

- It can also run on **gasoline-methanol blends** (up to 50% methanol) in emergency situations, which can extend range in fuel-scarce environments.

3. **Low Maintenance Costs (Compared to Modern Engines)**

- Spare parts are **relatively inexpensive** compared to newer turbocharged or fuel-injected engines.

- The **mechanical simplicity** (no fuel injection, fewer electronic components) reduces long-term maintenance complexity.

- Many **aftermarket support services** exist, including rebuild kits and conversion kits for different fuel types.

4. **Good Performance in High-Altitude and Hot Conditions**

- The R-915 performs well in **hot-and-high environments** due to its **direct fuel injection** (in the L6MB variant), which helps with cooling and power delivery.

- It was originally designed for **military use in tropical climates**, making it suitable for operations in regions with high ambient temperatures.

5. **Availability of Conversions and Upgrades**

- The engine can be **converted to run on alternative fuels** (e.g., **E85 ethanol, JP-8, or even diesel with modifications**), expanding operational flexibility.

- **Supercharger kits** are available for increased power output in high-altitude operations.

- **Direct-drive or gear-driven** configurations are possible, allowing for compatibility with different propeller systems.

6. **Proven Track Record in Military and Utility Applications**

- Used in **military trainers (e.g., Cessna T-37, North American T-6), bush planes, and agricultural aircraft**, the R-915 has a **long history of dependable service**.

- Many **vintage military aircraft** (e.g., T-6 Texan, AT-6, PT-19) still fly with this engine, demonstrating its longevity.

7. **Lower Purchase Cost (Compared to New Engines)**

- A **used R-915 L6MB** typically costs **significantly less** than a new Lycoming IO-360 or Continental IO-550, making it an attractive option for budget-conscious operators.

8. **Ease of Overhaul and DIY Repairability**

- Many mechanics and homebuilders find the engine **easier to overhaul** than modern engines with complex electronics.

- **Complete rebuild kits** are available, allowing for **in-house engine work** without relying solely on manufacturer support.

---

### **Cons**

1. **Higher Fuel Consumption**

- The R-915 is **thirsty** compared to modern inverted engines (e.g., Lycoming IO-360). Expect ** 12 15 GPH at cruise** (depending on propeller and altitude), which can be costly in modern aviation fuel markets.

- **Direct fuel injection** improves efficiency slightly, but it still lags behind modern fuel-injected engines.

2. **Noise and Vibration**

- Radial engines are **loud** (typically **90 100 dB at idle**), which can be problematic for **cabin comfort** and **neighborhood noise restrictions**.

- **Vibration levels** are higher than in modern smooth-running inverted engines, which may lead to **fatigue in the airframe over time** if not properly managed.

3. **Limited Modern Support and Parts Availability**

- While **not as rare as some vintage engines**, the R-915 is **less commonly maintained** than Lycoming or Continental engines, meaning **fewer certified mechanics** specialize in it.

- **OEM support from Jacobs Engines (now part of Pratt & Whitney Canada)** is **minimal** for older models, though aftermarket suppliers fill much of the gap.

- **Electronic ignition systems** (if not properly maintained) can be less reliable than modern **magneto-based or solid-state ignition** setups.

4. **Weight and Drag**

- Radial engines are **heavier** than modern inverted engines (typically **400 500 lbs dry**), increasing **takeoff distance and fuel burn**.

- The **large diameter** of the engine can create **more drag**, reducing cruise efficiency compared to streamlined inverted engines.

5. **Potential for Carbon Buildup and Cooling Issues**

- **Direct fuel injection** helps with cooling, but **poor maintenance** can lead to **carbon deposits** in the combustion chambers, reducing performance.

- **Air-cooled radials** require **proper cowl flaps and cooling airflow management** poor cooling can lead to **detonation or overheating**, especially in high-power settings.

6. **Limited Turbocharging Options (Without Modifications)**

- While **supercharger kits** exist, **turbocharging** is not natively supported without significant modifications, limiting high-altitude performance compared to turbocharged engines.

7. **Environmental and Regulatory Concerns**

- **Higher emissions** compared to modern fuel-injected engines, which may lead to **restrictions in noise-sensitive areas**.

- **Lead-based AVGAS requirements** (if not using 100LL) may be phased out in some regions, forcing operators to switch to higher-octane fuel.

8. **Resale Value and Market Demand**

- The **used market for R-915 engines is niche**, meaning **resale value depreciates faster** than more common engines like Lycoming IO-360s.

- **Financing options** may be limited compared to more mainstream aircraft engines.

---

### **Conclusion and Recommendation**

The **Jacobs R-915 L6MB (711-B)** is a **capable, rugged engine** with a **strong legacy in military and utility aviation**. It remains a **viable choice** for operators who prioritize **reliability, fuel flexibility, and low maintenance costs** over modern efficiency and noise reduction.

**Bush pilots** needing **off-airport performance** and **alternative fuel capability**.

**Homebuilders and experimental aircraft** looking for a **proven, repairable engine**.

**Operators in hot-and-high regions** where **direct fuel injection** provides an advantage.

**Budget-conscious buyers** who can tolerate **higher fuel burn and noise** for **long-term durability**.

**Military surplus or vintage aircraft restorations** (e.g., T-6, AT-6, PT-19).

**Cabin-class aircraft** where **noise and vibration** are major concerns.

**Operators seeking maximum fuel efficiency** (modern inverted engines are better).

**Those requiring extensive OEM support** (aftermarket reliance is necessary).

**Aircraft flying in **strictly regulated airspace** (due to emissions and noise).

If you are **operating in a rugged, fuel-flexible environment** and can **manage the higher fuel burn and noise**, the **R-915 L6MB is an excellent choice**. Its **proven reliability, alternative fuel capability, and lower maintenance costs** make it a **strong contender** for **utility, military surplus, or experimental aircraft**.

However, if **cabin comfort, fuel efficiency, and modern support** are priorities, a **Lycoming IO-360 or Continental IO-550** may be a better long-term investment.

**For the right operator, the R-915 remains a "workhorse" engine one that delivers when conventional engines might struggle.** Always ensure **proper maintenance, cooling management, and fuel quality** to maximize its lifespan.

Details:

Sodas used because of storage stains. Jacobs R-915 / L6MB aircraft Radial Engine piston, casting number 711-B, R52.

part #: r-915 prices

• $45.00-$48.50

specifications engineaviatio:

• brand: Jacobs Radial Engine
• mpn: 711-b
• part type: Piston
• compatible make: R-915 / L6mb

payments Engineaviatio:

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

returns Engineaviatio:

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

general Engineaviatio:

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

seller Engineaviatio:

• city: Plains, Georgia
• # reviews: 246
• rating: 100.0%

offer Engineaviatio:

• sold: 0
• started: April 19, 2026
• availability: In Stock
• quantity: 1
• options: Ship-to-home

shipping Engineaviatio:

• class: Standard
• carrier: USPS
• cost: $17.55
• type: Calculated
• transit: 5-11 Days
• service: USPS Ground Advantage

Jacobs Radial Engine L6MB Is Similar To:

• 569-7 Jacobs R755 Radial Engine Intake Pipe Nut Wrench (40.3% similar) Here is 1 each of Jacobs aircraft Engine P/N wrench, intake pipe nut in really good serviceable surplus condition. Used to install tighten remove intake pipe nuts on cylinders...(November 1st, 2015)
• 7392 Jacobs Aircraft Pistons Nos 392 11 Available (40.3% similar) If you feel shipping related charges are unreasonable please. Please feel free to ask. Under certain circumstances a return may be granted...(October 15th, 2015)
• R755-9 Jacobs Cessna Engine With Logbook (36.8% similar) 82 hours field overhaul done on may 1, 1971 Engine total time: 501. This is a used Jacobs R755-9 Engine that currently up for sale. I will not end offer early, so please do ask. Want more pictures...(May 18th, 2018)
• R755-b2m Jacobs Engine Mostly Complete Parts Lot (31.6% similar) I will not end offer early, so please do ask. This is a used Jacobs R755-B2M Engine parts lot that currently up for sale. Want more pictures. What you see in the pictures is exactly are getting...(May 18th, 2018)
• 4332 R755 Jacobs Engine Chrome Rocker Box Covers Set (32.1% similar) R755 Jacobs Engine chrome rocker box covers, set of 14, without gaskets...(May 29th, 2016)
• R-755 Jacobs Rotary Airplane Engine Coffee Table (36.1% similar) This is a beautiful Engine that I can not get pictures to give you the full effect. Sits 22 tall and is 48 wide at the top. This was made into a coffee table or one that could be used in a office or waiting area. It is heavy, probably in the lb range without the top. Will build a special crate for ...(October 10th, 2015)
• 1-209-10a 1-205 Time Rite Continental Jacobs Radial Engine Parts (30.9% similar) W670, R760, R975, c 90, c 145, o 300 a d, o 200 a f series Engines. The time rite scale can be used on various continental series Engines. The time rite arm can be used on various continental Engines. As always this is an original mfg'd item...(October 18th, 2016)