The DeSoto Fireflite III Convertible, specifically the 1958 facelift model equipped with the 5.9-liter V8 engine and TorqueFlite automatic transmission, represents a pivotal moment in the final years of the DeSoto marque. Produced from 1957 to 1958, this iteration of the Fireflite aimed to blend American luxury with performance, though it ultimately existed during a period of declining sales for the brand. It was positioned as a premium offering within the DeSoto lineup, appealing to buyers seeking a comfortable and stylish convertible experience. The Fireflite name itself evoked a sense of power and forward motion, aligning with the optimistic post-war American automotive landscape.
Technical Specifications
| Brand | DeSoto |
| Model | Fireflite |
| Generation | Fireflite III Convertible (facelift 1958) |
| Type (Engine) | 5.9 V8 (305 Hp) TorqueFlite |
| Start of production | 1957 |
| End of production | 1958 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 6 |
| Doors | 2 |
| Fuel Type | Petrol (Gasoline) |
| Power | 305 Hp @ 4600 rpm |
| Power per litre | 51.6 Hp/l |
| Torque | 542 Nm @ 2800 rpm / 399.76 lb.-ft. @ 2800 rpm |
| Engine displacement | 5916 cm3 / 361.02 cu. in. |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 104.65 mm / 4.12 in. |
| Piston Stroke | 85.85 mm / 3.38 in. |
| Compression ratio | 10:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Carburettor |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | OHV |
| Engine oil capacity | 3.8 l / 4.02 US qt | 3.34 UK qt |
| Coolant | 16.1 l / 17.01 US qt | 14.17 UK qt |
| Fuel tank capacity | 87 l / 22.98 US gal | 19.14 UK gal |
| Length | 5552 mm / 218.58 in. |
| Width | 1989 mm / 78.31 in. |
| Height | 1450 mm / 57.09 in. |
| Wheelbase | 3200 mm / 125.98 in. |
| Front track | 1549 mm / 60.98 in. |
| Rear track | 1516 mm / 59.69 in. |
| Front overhang | 892 mm / 35.12 in. |
| Rear overhang | 1461 mm / 57.52 in. |
| Ride height (ground clearance) | 140 mm / 5.51 in. |
| Minimum turning circle | 15.1 m / 49.54 ft. |
| Drivetrain Architecture | Rear wheel drive |
| Number of gears and type of gearbox | 3 gears, automatic transmission TorqueFlite |
| Front suspension | Independent coil spring |
| Rear suspension | Leaf spring |
| Front brakes | Drum, 305 mm |
| Rear brakes | Drum, 305 mm |
| Steering type | Worm-reduction unit |
Powertrain & Engine Architecture
The heart of the 1958 Fireflite III Convertible was the DeSoto 5.9-liter (361 cubic inch) V8 engine. This engine, designated within Chrysler’s engine family as the “RB” series, was a robust and relatively simple design. It featured a cast iron block and cylinder heads, with a two-barrel carburetor managing fuel delivery. The overhead valve (OHV) configuration utilized a single camshaft located in the engine block, operating the valves through pushrods and rocker arms. The 10:1 compression ratio contributed to the engine’s 305 horsepower output at 4,600 rpm and 542 Nm (399.76 lb-ft) of torque at 2,800 rpm. The TorqueFlite automatic transmission, a three-speed unit, was standard. This transmission was known for its durability and smooth shifting, though it lacked the sophistication of some contemporary automatic transmissions.
Driving Characteristics
The combination of the 305 hp V8 and the TorqueFlite automatic resulted in a driving experience focused on comfortable cruising rather than outright performance. While the engine provided ample power for highway passing and merging, the automatic transmission’s gear ratios were geared towards relaxed acceleration. Compared to the available manual transmission options in other DeSoto models, the automatic Fireflite felt less responsive. The large size and weight of the convertible body further contributed to a less agile feel. However, the Fireflite excelled in providing a smooth and quiet ride, typical of American convertibles of the era.
Equipment & Trim Levels
The Fireflite III Convertible was well-equipped for its time, offering a range of standard features designed to enhance comfort and convenience. Standard interior appointments included plush upholstery, often in two-tone color schemes, and a generously sized bench seat capable of accommodating three passengers. Power steering and power brakes were typically included. Optional extras included a radio, heater, and various trim enhancements, such as chrome accents and upgraded interior materials. The convertible top was power-operated, adding to the convenience. The dashboard layout was typical of the late 1950s, featuring a combination of analog gauges and prominent chrome trim.
Chassis & Braking
The Fireflite III Convertible utilized a body-on-frame construction, common for American cars of the period. The chassis featured an independent coil spring suspension at the front, providing a relatively comfortable ride. The rear suspension employed a traditional leaf spring setup, which was robust but less refined than the front suspension. Braking duties were handled by drum brakes on all four wheels, measuring 305 mm in diameter. While adequate for the car’s weight and performance, the drum brakes lacked the stopping power of disc brakes, which were becoming increasingly common on European sports cars.
Market Reception & Comparison
The 1958 DeSoto Fireflite III Convertible received mixed reviews from automotive critics. While praised for its styling and comfortable ride, it was often criticized for its lack of handling precision and relatively high price. Compared to other DeSoto models, such as the Adventurer, the Fireflite offered a more luxurious and comfortable experience, but at the expense of performance. Fuel economy was also a concern, typical of large-displacement V8 engines of the era. Reliability was generally good, but maintenance costs could be significant due to the complexity of the engine and the availability of parts.
Legacy
The DeSoto Fireflite III Convertible, and the DeSoto brand as a whole, ultimately faded into automotive history. Production ceased in 1961 due to declining sales and internal competition within the Chrysler Corporation. Today, the 1958 Fireflite Convertible is a sought-after classic car, particularly among collectors of American automobiles. The 5.9-liter V8 engine and TorqueFlite transmission, while not known for exceptional efficiency, are generally considered durable and reliable. Parts availability can be a challenge, but a dedicated community of DeSoto enthusiasts continues to support the preservation and restoration of these iconic vehicles. The Fireflite represents a bygone era of American automotive design and engineering, embodying the optimism and extravagance of the late 1950s.
