1968 Sunbeam Stiletto

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.

Symptoms: Rapid temperature gauge rise and coolant bubbling violently into the expansion bottle, Emulsified white sludge visible under the oil filler cap and on the dipstick...

Est. repair cost: £450–£1,200

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.

Symptoms: Spongy or crunching sensation when pressing gently across the vinyl roof panel, Rust blisters, bubbling, or brown staining around the edges of the vinyl roof seams...

Est. repair cost: £1,200–£4,000

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.

Symptoms: Cooling temperature gauge creeping steadily toward maximum during slow urban driving, Coolant weeping from the water pump bearing weep hole on the rear of the engine...

Est. repair cost: £220–£550

The Stiletto's rear-mounted transaxle features synchromesh on all four forward gears, but the high-revving nature of the 875cc Sport engine encourages aggressive downshifting from enthusiast drivers. Over time, the brass synchromesh baulk rings wear smooth, particularly on second gear, leading to grating gear changes on downshifts. Additionally, worn selector fork pads and fatigued detent springs cause the transaxle to jump out of second gear on deceleration or engine overrun. Rebuilding the compact transaxle requires specialised Rootes knowledge and scarce replacement gear clusters.

Symptoms: Grinding or crunching sound when shifting rapidly from third down into second gear, Gear lever popping violently out of second gear when releasing the throttle on overrun...

Est. repair cost: £350–£900