1978 Triumph Dolomite 1.5L Petrol · TUN 377T

The 16-valve Sprint and 8-valve 1850 slant-four engines utilise an aluminium cylinder head mounted atop an inclined cast-iron block. The diagonal angled head studs and high thermal stresses make the engine exceptionally vulnerable to overheating. A lack of high-specification corrosion-inhibited antifreeze allows electrolytic corrosion of the aluminium castings, silting up the radiator and blowing the head gasket.

The monocoque shell of the Dolomite suffers from severe structural corrosion in the hidden junction where the windscreen A-pillar meets the bulkhead and inner wing. Water draining through deteriorated windscreen rubbers and blocked scuttle vents collects in this structural joint, rusting through multiple panels into the driver footwells and weakening the passenger safety cell.

On Dolomite Sprint models, the twin 1.75-inch SU HS6 carburettors are isolated from engine vibration by rubber-to-metal sandwich mounting blocks. Over time, heat soak and fuel vapours cause the rubber to perish, split and delaminate. This admits unmetered air into the intake manifold, creating a dangerous lean fuel-air mixture that causes erratic idling, hesitation, and burnt exhaust valves.