Quick search, the C series was in fact the straight six as used in the Austin Healey 3000. From Wikipedia:
"The BMC C-Series was a straight-6 automobile engine produced from 1954 to 1971. Unlike the Austin-designed A-Series and B-Series engines, it came from the Morris Engines drawing office in Coventry and therefore differed significantly in its layout and design from the two other designs which were closely related. Displacement was 2.6 to 2.9 L with an undersquare stroke of 88.9 mm, bored out to increase capacity."
Breif info on the A series:
"Austin Motor Company's small straight-4 automobile engine, the A-Series, is one of the most common in the world. Launched in 1951 with the Austin A30, production lasted until 2000 in the Mini. It used a cast-iron block and cylinder head, and a steel crankshaft with 3 main bearings. The camshaft ran in the cylinder block, driven by a single-row chain for most applications, and with tappets sliding in the block, accessible through pressed steel side covers for most applications, and with overhead valves operated through rockers. The cylinder head for the overhead-valve version of the A-Series engine was designed by Harry Weslake a cylinder head specialist famed for his involvement in SS (Jaguar) engines and several F1 title winning engines. Although a 'clean sheet' design the A-Series owed much to established Austin engine design practise, resembling in general design (including the Weslake head) and overall appearance a scaled-down version of the 1200cc overhead-valve engine first seen in the Austin A40 Devon which would form the basis of the later B-Series engine."
And B series:
"The precursor of the "B" series engine was a 1200 cc Overhead Valve (OHV) engine which was used in the 1947-1952 Austin A40 Devon, and, in slightly modified form, in the 1953 Austin A40 Somerset. This engine had the same basic dimensions as one of Austin's pre-war sidevalve engines but to an all-new OHV design which had many features copied from the Chevrolet 235 straight-six engine used on military trucks that the Austin works had overhauled during the Second World War. These features included the valve gear and especially the siamesed cylinder head ports. Austin realised that eventually they would need an engine that could power many of its forthcoming medium-sized cars, and this would require an engine of at least 1500 cc capacity. Since the A40 Devon engine could not have its capacity enlarged, a new engine needed to be designed and built.
The design of this new engine commenced around January 1952, and was designated as the "B" series."
Surprisingly, the B series is also listed as a straight 6 configuration, as well as the well known inline 4...
Edited by mini_pooper, 08 May 2018 - 09:00 PM.