The design dates back to 1952 when MG designer Syd Enever created a streamlined body for George Philips' TD Le Mans car. The problem with this car was the high seating position of the driver because of the limitations of using the TD chassis. A new chassis was designed with the side members further apart and the floor attached to the bottom rather than the top of the frame sections. A prototype was built and shown to the BMC chairman Leonard Lord. Lord turned down the idea of producing the new car as he had just signed a deal with Donald Healey to produce Austin-Healey cars.
Falling sales of the traditional MG models caused a change of mind and the car, initially to be called the UA-series, was brought back. As it was so different from the older MG models it was called the MGA, the "first of a new line" to quote the contemporary advertising. There was also a new engine available so the car did not have the originally intended XPAG unit but was fitted with the BMC corporate B-Series type allowing a lower bonnet line. It was a body-on-frame design and used the straight-4 "B series" engine from the MG Magnette saloon driving the rear wheels through a 4 speed gearbox. Suspension was independent with coil springs and wishbones at the front and a rigid axle with semi-elliptic springs at the rear. Steering was by rack and pinion and was not power assisted. The car was available with either wire spoked or steel disc road wheels. The 1,489 cc engine produced 68 hp (51 kW) at first, but was soon uprated to 72 hp (54 kW). Lockheed hydraulic drum brakes were used on all wheels. A coupé version was also produced, bringing the total production of standard MGAs to 58,750.
A high-performance Twin-Cam model was added for 1958. It used a high compression (9.9:1 later 8.3:1) DOHC aluminium cylinder head version of the B-Series engine producing 108 hp (82 kW) (100 BHP in the low compression version). Four wheel disc brakes by Dunlop were also fitted, along with Dunlop peg drive knock-off steel wheels akin to the wheels used on racing Jaguars (wire spoked wheels were never fitted to the Twin Cam). The temperamental engine was notorious for warranty problems during the course of production, however, and sales were poor. Ironically, the source of the problem was only discovered after production had ended and many restored Twincam cars are running more reliably today than they ever did during production. The Twin-Cam was dropped in 1960 after 2,111 had been produced. The car can best be distinguished from the pushrod models by its centre lock steel road wheels.
In May 1959 the standard cars also received an updated engine, now at 1,588 cc producing 78 bhp. Front discs were fitted, but drums remained in the rear. 31,501 were produced in less than three years. Externally the car is very similar to the 1500 with differences including: Amber or white (depending on market) front turn indicators shared with white parking lamps, separate stop/tail and turn lamps in the rear, and 1600 badging on the boot and the cowl. A number of 1600 De Luxe versions were produced with leftover special wheels and four wheel disc brakes of the departed Twin-Cam, or using complete modified Twincam chassis left redundant by the discontinuance of that model. Seventy roadsters and 12 coupés were built.
The engine size was increased again to 1,622 cc by increasing the bore from 75.4 mm to 76.2 mm for the 1961 Mark II MGA. It also had a higher ratio 4:1 rear axle which made for more relaxed high speed driving. An inset grille and Morris Mini tail lamps appearing horizontally below the deck lid were the most obvious visual changes. 8,198 Mark II roadsters and 521 coupés were built. As with the 1600 De Luxe, there were also some Mark II De Luxe versions with 290 roadsters and 23 coupés made.Source: Wikipedia.