Sunbeam Stiletto
Introduced in October 1967, the Sunbeam Stiletto was the sporting flagship of the Hillman Imp family, combining the rakish fastback coupe bodyshell of the Californian with the high-output mechanicals of the Imp Sport. Powered by the rev-happy 875cc all-aluminium overhead-camshaft engine developed from Coventry Climax fire-pump origins, the Stiletto featured twin Stromberg CD125 carburettors, a high-lift camshaft, and 51 bhp at 6,100 rpm. Visually distinguished by four round headlights, a black vinyl roof, and a bespoke sports dashboard with full round instrumentation, the lightweight rear-engined coupe offered agile handling and punchy performance. Over its five-year production run at Rootes' Linwood plant in Scotland, approximately 9,000 Stilettos were built. Today, surviving cars are actively cherished through The Imp Club. Buying a Stiletto requires thorough scrutiny of the rear cooling system, engine head integrity, and rust under the factory vinyl roof, with pristine survivors commanding £6,500–£12,000.
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Common Faults & Reliability
These are the most common documented problems for the Sunbeam Stiletto, sorted by their typical impact and frequency.
Coventry Climax-derived alloy engine airlocks and head gasket failure
high severityThe Stiletto's rear-mounted 875cc all-aluminium engine is derived from the Coventry Climax FWMA racing and fire-pump unit. Featuring a wet-liner design and a high 10:1 compression ratio on the twin-carburettor Sport specification, it is extremely sensitive to coolant maintenance. Because the radiator is mounted at the rear next to the engine, bleeding the cooling system after servicing is notoriously difficult. If an airlock develops, or if the coolant level drops, localized overheating causes the cylinder head to warp instantly, blowing the composite head gasket and contaminating the engine oil.
Rear-mounted cooling system silting, water pump wear and overheating
medium severityThe compact rear-engine layout of the Stiletto relies on a tight engine-driven cooling fan pulling air through a rear-mounted radiator. If owners historic operated the car on plain tap water instead of a 50/50 glycol inhibitor mix, the narrow radiator matrix tubes and aluminium water galleries become clogged with mineral scale and corrosion debris. Additionally, the high-revving water pump seals wear and leak, causing chronic coolant loss. Restricted circulation leads to rapid overheating in traffic, putting the delicate all-aluminium engine block and liners at severe risk of seizure.
Vinyl roof panel corrosion and sill structure rot
high severityFactory Sunbeam Stilettos came standard with an exterior black vinyl roof covering that lent the coupe a stylish GT appearance. Over decades of British weather, moisture seeps through micro-cracks in the vinyl and around the glued seams, where it is trapped against the steel roof skin. The steel rusts undetected until perforations bubble up or the roof collapses under light pressure. Concurrently, road salt attacks the structural three-piece box sills, floorpans, and rear suspension crossmember mounts. Restoring a rusted Stiletto shell requires complex structural welding and bespoke panel beating.
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