23/10/2015
The 1962 Sunbeam Alpine is a classic British sports car that continues to capture the hearts of enthusiasts. Its distinctive styling and engaging driving experience make it a sought-after vehicle. This article delves into the technical heart of the 1962 model, exploring its engine, chassis, and other key components, as well as touching upon popular modifications and common queries from owners.
The Heart of the Alpine: Engine Specifications
At the core of the 1962 Sunbeam Alpine lies a robust four-cylinder engine. This unit is characterised by its five-bearing crankshaft, which provides excellent durability and smooth operation. The cylinder head is crafted from aluminium, a nod to performance and weight saving for its era. Push-rod operated, inclined overhead valves manage the intake and exhaust cycles.
Fuel delivery is handled by a pair of Zenith/Stromberg 150 CD carburettors, known for their reliability and performance. To minimise vibration and enhance the driving experience, the engine is mounted on four rubber mountings. The crankcase benefits from a sealed ventilation system, and an oil cooler is fitted to maintain optimal engine temperatures during spirited driving.
Engine Performance Figures:
The bore and stroke measure 3.21 inches by 3.25 inches (81.5 mm x 82.55 mm), giving a displacement of 105.2 cubic inches (1,725 c.c.). This powerplant produces a healthy 100 brake horsepower at 5,500 r.p.m., with a maximum torque of 110.2 lb. ft. at 3,700 r.p.m. The compression ratio stands at 9.2:1, indicating a good balance between power and efficiency for its time.
Ignition and Cooling Systems:
The ignition system is a conventional coil and distributor setup, featuring both centrifugal and vacuum control for ignition timing, ensuring optimal performance across different engine speeds and loads. Champion N9Y sparking plugs are specified. The cooling system employs a centrifugal pump and a four-bladed fan, with thermostatic control for rapid engine warm-up. A vertical flow radiator, complete with a header tank, ensures efficient heat dissipation.
Drivetrain and Chassis Excellence
The Alpine's drivetrain is designed for enjoyable performance. The clutch is a 7 1/2 inch Borg and Beck diaphragm unit with strap drive, operated hydraulically via a pendant pedal for a smooth and progressive engagement.
Gearbox and Rear Axle:
A four-speed manual gearbox with reverse is featured, incorporating control ring synchromesh on all forward gears for effortless shifting. The gear lever is centrally mounted on the floor for intuitive control. The rear axle is a semi-floating design with a hypoid final drive, featuring an axle ratio of 3.89:1. The overall gear ratios provide a good spread of performance, from strong initial acceleration to comfortable cruising speeds.
| Gear | Ratio |
|---|---|
| Top | 3.89: 1 |
| Third | 5.04: 1 |
| Second | 7.75: 1 |
| First | 12.14: 1 |
| Reverse | 12.92: 1 |
Chassis and Construction:
The 1962 Alpine boasts a unitary construction of chassis and body. This innovative approach, incorporating 'X' bracing, provides exceptional strength and rigidity while maintaining a light overall weight and a low centre of gravity, crucial for agile handling.
Suspension and Steering: A Focus on Handling
The suspension system is a key contributor to the Alpine's renowned handling characteristics.
Front Suspension:
The front suspension is fully independent, utilising silico-manganese coil springs and swinging links. Telescopic shock absorbers are housed centrally within the coil springs, offering effective damping. A torsion bar sway eliminator is fitted between the lower suspension links, reducing body roll during cornering. A significant benefit of this design is the elimination of all greasing points, simplifying maintenance.
Rear Suspension:
At the rear, semi-elliptic leaf springs are employed, a traditional yet effective solution for providing a compliant ride and supporting the rear axle. Direct-acting telescopic shock absorbers ensure complete control over wheel movement.
Steering System:
The steering is a Burman recirculating ball type, known for its precise and predictable response. A three-piece symmetrical track rod linkage contributes to accurate wheel alignment. Like the suspension, the steering system also features no greasing points. The steering wheel itself offers 2 1/2 inches of 'telescopic' adjustment, has two sprung spokes, and a chromium-plated horn ring. The GT model features a wood-rim wheel.
Braking and Wheels
Safety is paramount, and the Alpine is equipped with a capable braking system.
Brakes:
The front brakes are Girling 9.85-inch diameter disc brakes, offering superior stopping power and fade resistance. At the rear, 9-inch diameter brake drums provide effective braking. The total swept area of the braking system is 295 square inches. The handbrake operates mechanically on the rear wheels, with the lever conveniently located at the side of the driver's seat.
Wheels and Tyres:
The Alpine is fitted with five pressed steel wheels featuring cooling apertures. Four of these are adorned with polished nave plates and wheel trims. The spare wheel is housed vertically within the luggage compartment. The specified tyres are 6.00 x 13 inch Dunlop nylon cord tubeless, providing a good balance of grip and ride comfort.
Electrical System and Equipment
The electrical system is a 12-volt setup, powered by a 38 amp-hour battery located under the occasional seat. The starter is engaged via a solenoid from a facia-mounted switch. A 35-amp alternator provides charging current. Lighting is comprehensive, including powerful double-dip headlights with a foot dimmer control, separate sidelamps, integrated twin stop/tail lamps with reflectors, and self-cancelling flashing indicators operated by a steering column lever that also incorporates a headlamp flasher. A map light is also included.
Standard Equipment:
The Alpine comes well-equipped for its era, featuring twin wind-tone horns, two-speed windscreen wipers, and screen washers. A comprehensive set of warning lights indicates ignition, main beam, and direction indicators. The dashboard includes a speedometer with trip and mileage recorders, a revolution counter, oil pressure gauge, water temperature gauge, and a fuel gauge. For safety, anchorages for seat belts are provided, along with a passenger's grab handle and a ventilation system. The GT model further enhances comfort with a heater, carpeted floor, sun visors, and door-operated courtesy lights as standard.
Optional Overdrive Unit
For owners seeking to further enhance their driving pleasure, a Laycock-de Normanville overdrive unit was available at extra cost. This unit was designed for use in top and third gears and operated in conjunction with a final drive ratio of 4.22:1. It was crucial to specify this option at the time of ordering, as it was fitted during production.
Common Queries and Modifications: The 1725 Engine in a Rapier
A frequent topic among Sunbeam enthusiasts revolves around engine swaps and upgrades. The 1725cc engine, as found in the Alpine, is also a popular choice for enhancing the performance of other Rootes Group cars, such as the Sunbeam Rapier.
Can a 1725 Engine Go in a Rapier?
Yes, a 1725cc engine can be fitted into a Sunbeam Rapier, and indeed, it was fitted as standard to later models. Discussions among owners highlight the feasibility of transplanting a 1725cc Holbay unit, often with Weber carburettors and performance exhaust systems, into earlier Rapiers. Key considerations include:
- Engine Mounting: The 1725cc engine was fitted upright in Rapiers, whereas in some Alpine variants, it was canted. Adapting engine mountings is often necessary.
- Carburettor Clearance: Fitting twin Weber carburettors, especially with performance inlet manifolds, can be tight. Some owners opt for custom-made short inlet manifolds or modify existing ones to achieve a better fit and angle.
- Gearbox Compatibility: The gearbox from a 1725cc engine, particularly from Fastback Rapiers, is generally compatible. However, differences in input/output shaft splines and bellhousing length may require attention. The clutch and flywheel may also need consideration, with some suggesting the standard 7.5" clutch being adequate.
- Propeller Shaft: If the gearbox or rear axle ratios are changed, the propeller shaft may need to be shortened or adapted.
- Rallying Regulations: For those involved in classic rallying, modifications like Weber carburettors may require waivers or may be disallowed depending on the specific regulations and the period being represented.
The discussion indicates that while the swap is achievable, careful planning and potential custom fabrication, such as modifying inlet manifolds or adapting the bellhousing, are often required. The goal is typically to achieve a neat, reversible installation that enhances performance, particularly for rallying applications.
Rebuilding a 1725cc Engine:
When undertaking a rebuild of a 1725cc engine, owners often seek advice on achieving optimal results. Common practices include:
- Cylinder Head Work: Cleaning up ports and combustion chambers, along with a professional three-angle valve job, can significantly improve flow and efficiency.
- Camshafts: Regrinding the existing camshaft or fitting an aftermarket performance camshaft can yield noticeable gains.
- Bore and Piston Check: It is crucial to have the engine block checked for bore wear and ovality. If significant wear is present, boring the block and fitting new pistons may be necessary.
- Bearings and Gaskets: Replacing main and big-end bearings, along with all necessary gaskets, is standard procedure for a comprehensive rebuild.
- Oil Pump: Testing the oil pump for proper function before installation is recommended.
The overall consensus is that for a street car, extensive modifications like Vizard mods might not be essential, with careful porting and a good valve job providing substantial improvements.
Conclusion
The 1962 Sunbeam Alpine remains a captivating classic, offering a rewarding driving experience coupled with a rich technical heritage. Its well-engineered components, from the lively 1725cc engine to its agile suspension, make it a joy to own and drive. For those looking to enhance performance, the potential for upgrades, such as fitting a 1725cc engine into a Rapier, offers exciting possibilities, though careful consideration of compatibility and fabrication is key.
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