Racing version of 'K'-type (winner of 1933 Ulster T.T.). 1087-cc, 6-cylinder, ohc engine, supercharged, 120 bhp at 6500 rpm. Four-speed preselector gearbox. Half-eliptic springs. Centre-lock wire wheels. Two-seater racing body; flat tail with slab tank (1933) or pointed tail (1934). Number built: 32.

See magazine articles:
The Supercharged Magnette - Autocar August 11, 1933 (1.4-MB pdf)
A Brace of M.G. K3 Magnettes - Autocar December 19, 1947 (1.0-MB pdf)
MG K3 from Thoroughbred & Classic Cars, October 1975 (1.4-MB pdf)