The DeSoto Firesweep I Convertible with the PowerPack 5.7 V8 and TorqueFlite automatic transmission represents a pivotal, though short-lived, moment in the American automotive landscape of the late 1950s. Produced for only two model years, 1957 and 1958, the Firesweep was DeSoto’s attempt to capture the burgeoning market for stylish, powerful, and comfortable personal cars. Positioned as a premium offering within the DeSoto lineup, it aimed to compete with models from Buick, Oldsmobile, and Mercury. The Firesweep Convertible, in particular, embodied the optimism and extravagance of the era, offering open-air motoring with a substantial dose of American V8 power.
Technical Specifications
| Brand | DeSoto |
| Model | Firesweep |
| Generation | Firesweep I Convertible |
| Type (Engine) | PowerPack 5.7 V8 (295 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 | 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 | 3 gears, automatic transmission TorqueFlite |
| 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 DeSoto’s “PowerPack” 5.7-liter (349.97 cubic inch) V8 engine. This engine, based on the Chrysler Hemi engine family, featured a cast iron block and aluminum cylinder heads. The 10:1 compression ratio and a four-barrel carburetor contributed to its respectable 295 horsepower output at 4600 rpm and 385 lb-ft of torque at 2800 rpm. The engine utilized an overhead valve (OHV) configuration with two valves per cylinder. The TorqueFlite automatic transmission, a three-speed unit, was the sole transmission option for the Firesweep Convertible. This transmission was known for its smoothness and durability, and it was a key selling point for buyers seeking a comfortable and effortless driving experience. The TorqueFlite’s gear ratios were optimized for both cruising and acceleration, providing a balance between performance and fuel economy, though fuel economy was not a primary concern for buyers in this segment.
Driving Characteristics
The combination of the 295 hp V8 and the TorqueFlite automatic resulted in a surprisingly capable performer for its time. While not a sports car, the Firesweep Convertible offered brisk acceleration and comfortable highway cruising. The automatic transmission, while smooth, did rob some of the engine’s potential, especially compared to the available manual transmission options in other DeSoto models. The gear ratios were spaced to prioritize smooth shifts and relaxed driving, rather than outright performance. The car’s substantial weight (approximately 3,800 lbs) also limited its agility. However, the ample torque of the V8 engine meant that passing maneuvers were executed with confidence. The ride quality was generally good, thanks to the independent coil spring front suspension, but the leaf spring rear suspension could be somewhat bouncy on rough roads.
Equipment & Trim Levels
The Firesweep Convertible was well-equipped for its era, offering a range of standard features designed to appeal to discerning buyers. Standard equipment included power steering, power brakes, a heater, and a deluxe interior with cloth and vinyl upholstery. The dashboard featured a full-width instrument panel with prominent gauges for speed, fuel, temperature, and oil pressure. Optional extras included power windows, power seats, a radio, and whitewall tires. The Firesweep Convertible was available in a variety of vibrant colors, and the interior trim could be customized with different color combinations. The overall aesthetic was one of understated elegance, with chrome accents and a focus on comfort and convenience.
Chassis & Braking
The Firesweep Convertible rode on a conventional body-on-frame chassis. The front suspension utilized independent coil springs, providing a relatively comfortable ride. The rear suspension employed leaf springs, which were more robust but less refined. Braking was accomplished via drum brakes on all four wheels, measuring 279mm in diameter. While adequate for the time, the drum brakes lacked the stopping power of modern disc brakes. Steering was handled by a worm-reduction unit, which provided a relatively heavy but precise feel. The car’s relatively wide track and long wheelbase contributed to its stability and handling.
Market Reception & Comparison
The Firesweep Convertible received generally positive reviews from automotive critics. It was praised for its stylish design, comfortable ride, and powerful engine. However, some critics noted that the car was somewhat expensive compared to its competitors. Compared to other DeSoto models, the Firesweep Convertible was the most luxurious and expensive offering. The Firesweep sedan, for example, was more affordable and targeted a broader audience. The Firesweep’s fuel economy was typical for a large American V8 of the era, averaging around 15-18 mpg. Reliability was generally good, although the carburetor could sometimes require adjustment.
Legacy
The DeSoto Firesweep I Convertible, despite its short production run, remains a desirable classic car today. Its striking design and powerful V8 engine have earned it a loyal following among collectors. The TorqueFlite automatic transmission, while not as sought after by performance enthusiasts, is known for its durability and ease of maintenance. Finding well-preserved examples can be challenging, as many were driven hard and neglected over the years. However, parts availability is generally good, thanks to the shared components with other Chrysler products. The Firesweep Convertible represents a fleeting moment of optimism and extravagance in American automotive history, and it continues to captivate enthusiasts with its timeless style and powerful presence.
