The MGA was manufactured by MG at Abingdon-on-Thames from 1955 to 1962, replacing the traditional upright T-series cars with a sleek, aerodynamic design that became the best-selling British sports car of its era. Over 101,000 MGAs were built across four distinct variants, the 1500, the Twin Cam, the 1600, and the 1600 Mk II, each with specific parts differences that are essential to understand when selecting replacement components. The MGA uses a separate steel chassis with a bolt-on steel body, fundamentally different from the monocoque construction of the later MGB, and this distinction affects virtually every aspect of parts selection from bodywork through to suspension and structural components.
Four Variants, Four Specifications
The MGA 1500 (1955 to 1959) established the platform with its 1,489cc BMC B-series pushrod engine producing approximately 68 bhp at launch, later uprated to 72 bhp, with Lockheed drum brakes on all four wheels and a four-speed gearbox without synchromesh on first gear. The body was available as a roadster from launch, with the coupé following in September 1956. Standard wheels were bolt-on pressed steel disc wheels, with wire wheels available as an optional extra. The MGA Twin Cam (1958 to 1960) was the high-performance variant, powered by a 1,588cc twin overhead camshaft engine producing approximately 108 bhp.
It is visually distinguished by its Dunlop centre-lock disc wheels and Dunlop four-wheel disc brakes, the only MGA variant with discs on all four corners. Approximately 2,111 Twin Cams were built. Many Twin Cam-specific parts, particularly the engine, brakes, and wheels, are unique and not interchangeable with the pushrod cars. The MGA 1600 (1959 to 1961) brought the most significant mechanical change to the standard car: Lockheed front disc brakes replaced the all-drum arrangement of the 1500, while rear drum brakes were retained.
The engine was enlarged to 1,588cc producing approximately 79.5 bhp. Externally, the 1600 introduced larger sidelamps with a separate indicator bulb and part-amber lenses on UK-market cars, requiring redesigned front wings to accommodate them, along with enlarged rear lamps featuring separate indicator fittings. The MGA 1600 Mk II (1961 to 1962) was the final variant, with the engine further enlarged to 1,622cc and a higher compression ratio producing approximately 90 bhp. It is most readily identified by its recessed front grille and the relocated horizontal rear lamp clusters mounted below the boot lid rather than on the wings.
Approximately 8,719 Mk II cars were produced, making it the lowest-production pushrod MGA variant.
Identifying Your MGA
Correct identification is the starting point for all parts selection. The chassis number is located on the horizontal top surface of the box-section crossmember at the rear of the gearbox, on the right-hand side of the gearbox cover tunnel. On pushrod models, the chassis number is a five- or six-figure number with no prefix. On Twin Cam models, the number is typically three or four figures only.
The engine number is stamped on a plate rivetted to a lip at the top of the cylinder block on the right-hand side, just below the spark plugs between cylinders two and three. The engine number prefix identifies both the engine capacity and specification: 15GB and 15GD for the 1,489cc 1500 engines, 16GA for the 1,588cc 1600, 16GC for the 1,622cc Mk II, and 16GB for the Twin Cam. Because the MGA is now over sixty years old, many cars have had engines, gearboxes, or other major components replaced during their lives. It is not uncommon to find an MGA fitted with a non-original B-series engine from another BMC vehicle, or a Twin Cam that has had its original engine replaced with a pushrod unit.
Checking the engine number prefix against the chassis number is essential to confirm the car's true specification before ordering parts.
B-Series Engine Commonality
The MGA's BMC B-series engine shares its fundamental architecture with the later MGB engine, and some internal components, bearings, gaskets, timing chain components, and oil filtration parts, may be shared or closely related between the MGA and early MGB. However, the MGA is a fundamentally different platform from the MGB, with its own chassis, body, suspension geometry, brake systems, and electrical architecture.
Where B-series components are shared between models, this is noted in the relevant sections of this catalogue. Where components are MGA-specific, this is equally important to understand to avoid ordering incompatible parts.
Positive Earth Electrical System
All MGAs left the factory with a positive earth electrical system. This affects the selection of every electrical component on the car, from the dynamo and regulator through to lighting, ignition, gauges, and wiring.