1971 Sunbeam Stiletto 0.9L Petrol · WCA 18K

The 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.

The 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.

Factory 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.