The DeSoto Firesweep I Convertible, equipped with the PowerPack 5.7 V8 engine and PowerFlite automatic transmission, represented a significant offering in the American luxury car market during its brief production run from 1957 to 1958. Positioned as a premium offering within the DeSoto lineup, the Firesweep aimed to combine stylish design with robust V8 performance. It was built on the Chrysler corporation’s forward-looking platform, sharing components with other Chrysler-branded vehicles, but distinguished by its unique styling and upscale appointments. This particular configuration, pairing the 295 horsepower V8 with the two-speed PowerFlite automatic, was designed to appeal to buyers seeking a blend of power and convenience.
Technical Specifications
| Brand | DeSoto |
| Model | Firesweep |
| Generation | Firesweep I Convertible |
| Type (Engine) | PowerPack 5.7 V8 (295 Hp) PowerFlite |
| 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 | 295 Hp @ 4600 rpm |
| Power per litre | 51.4 Hp/l |
| Torque | 522 Nm @ 2800 rpm / 385.01 lb.-ft. @ 2800 rpm |
| Engine displacement | 5735 cm3 / 349.97 cu. in. |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 103.12 mm / 4.06 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 | 5499 mm / 216.5 in. |
| Width | 1989 mm / 78.31 in. |
| Height | 1443 mm / 56.81 in. |
| Wheelbase | 3099 mm / 122.01 in. |
| Front track | 1547 mm / 60.91 in. |
| Rear (Back) track | 1516 mm / 59.69 in. |
| Front overhang | 940 mm / 37.01 in. |
| Rear overhang | 1461 mm / 57.52 in. |
| Ride height (ground clearance) | 142 mm / 5.59 in. |
| Minimum turning circle (turning diameter) | 14.2 m / 46.59 ft. |
| Approach angle | 16.5° |
| Departure angle | 11.4° |
| Ramp-over (brakeover) angle | 10.5° |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 2 gears, automatic transmission PowerFlite |
| Front suspension | Independent coil spring |
| Rear suspension | Leaf spring |
| Front brakes | Drum, 279 mm |
| Rear brakes | Drum, 279 mm |
| Steering type | Worm-reduction unit |
Powertrain & Engine Architecture
The heart of the Firesweep I Convertible was the DeSoto PowerPack 5.7 V8 engine. This engine, displacing 349.97 cubic inches (5735 cm3), featured a cast iron block and aluminum cylinder heads. It utilized a carbureted fuel system, typical for the era, and an overhead valve (OHV) valvetrain. The 10:1 compression ratio contributed to its respectable 295 horsepower output at 4600 rpm and 385 lb-ft of torque at 2800 rpm. The PowerFlite automatic transmission, a two-speed unit, was designed to provide smooth and effortless shifting. While not as sophisticated as some contemporary automatics, it was known for its durability and simplicity. The PowerFlite’s gear ratios were optimized for cruising, prioritizing comfort over outright acceleration.
Driving Characteristics
The combination of the 295 hp V8 and the PowerFlite automatic resulted in a driving experience geared towards comfortable cruising rather than sporty performance. Acceleration was adequate for the time, but the two-speed automatic limited the engine’s ability to rev freely. The PowerFlite’s shift points were relatively low, prioritizing smooth operation over maximizing power. Compared to the available manual transmission options in other DeSoto models, the PowerFlite-equipped Firesweep offered a more relaxed driving experience, appealing to buyers who valued convenience over driver engagement. The rear-wheel-drive layout and leaf spring rear suspension provided a stable ride, but handling was not particularly sharp by modern standards.
Equipment & Trim Levels
The Firesweep I 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 cabin capable of seating six passengers. Power steering and power brakes were typically included. Optional extras included a radio, heater, and various trim enhancements. The Firesweep’s dashboard featured a prominent instrument cluster with gauges for speed, fuel level, temperature, and oil pressure. The exterior was characterized by its distinctive tailfin design and generous chrome accents, reflecting the styling trends of the late 1950s.
Chassis & Braking
The Firesweep I Convertible utilized a body-on-frame construction, common for American cars of the era. The front suspension featured independent coil springs, providing a relatively comfortable ride. The rear suspension employed leaf springs, which were robust and capable of handling the car’s weight. Braking duties were handled by drum brakes on all four wheels, measuring 279 mm in diameter. While adequate for the time, the drum brakes lacked the stopping power and fade resistance of modern disc brake systems. Steering was accomplished via a worm-reduction unit, which provided relatively heavy but precise steering feel.
Market Reception & Comparison
The DeSoto Firesweep I Convertible was generally well-received by critics, who praised its stylish design and comfortable ride. However, some reviewers noted that the PowerFlite automatic transmission could feel sluggish compared to manual transmissions. Compared to other DeSoto models, such as the Adventurer, the Firesweep offered a more luxurious and refined experience. Fuel economy, typical for a large American V8 of the era, was relatively poor. Reliability was generally good, but maintenance costs could be high due to the complexity of the V8 engine and the need for regular servicing.
Legacy
The DeSoto Firesweep I Convertible, while only produced for two years, remains a desirable classic car today. The PowerPack 5.7 V8 engine and PowerFlite automatic transmission, while not the most technologically advanced components, are known for their durability and relative simplicity. Finding parts can be challenging, but a dedicated community of DeSoto enthusiasts exists to support restoration efforts. The Firesweep’s distinctive styling and comfortable ride continue to appeal to collectors and enthusiasts, ensuring its place in automotive history. In the used car market, well-maintained examples command significant prices, reflecting their rarity and historical significance.
