The 1500cc air filter uses a single large assembly that serves both SU HS4 carburettors simultaneously. The assembly contains the paper filter elements within a common housing, sealed by a backplate with a gasket.
This is a significantly different arrangement from the 1275cc’s individual filters.
1500cc Air Filters Fitting
Air reaches each carburettor through flexible air hoses of approximately 23.5 inches in length, connecting the filter housing outlets to adaptor fittings on each carburettor intake. The assembly is mounted to the inlet manifold area by bolts with spring washers, and a pipe clip secures the air intake ducting to the housing.
1500 Filter Elements
The 1500 filter elements are physically larger than the 1275cc items and are not interchangeable. The backplate seal should be inspected whenever the elements are changed, a deteriorated seal allows unfiltered air to bypass the element and enter the carburettors directly. Unfiltered air carries abrasive dust and grit particles that accelerate bore, ring, and valve guide wear. The elements should be replaced at each major service, and more frequently if the car is used on dusty roads or stored in an environment where airborne particles are present.