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A BRIEF HISTORY OF THE "B" SERIES ENGINE

B.M.C "B" Series
       1 1/2 Litres in many guises

Briefly described, the British Motor Corporation's "B" series engine is a straight-forward 1 1/2 litre, four cylinder. The "B" series power unit has been put to a multitude of tasks in it's twelve years of existence. It has acquitted itself well in each instance. The "B" series engine has seen service in sedate saloons, record-breaking sports cars, light commercials and sundry marine and industrial applications.

It's size has varied from 1200 to 1800 cubic centimetres, it has been adorned with twin overhead camshafts and, in Australia, given two extra cylinders to power the Austin "Freeway" and Wolseley 24/80. It is hardly likely that the four cylinder capacity can be increased beyond 1800 c.c. without the pistons touching each other. The degree of versatility inherent in the basic design can be appreciated by a comparison of its numerous development stages with the rather limited changes GM-H made to the original Holden engine before supplanting it with an entirely new design.

THE AUSTIN A40 - MORRIS MINOR TIE-UP
The linking of Britain's two automotive giants, Morris and Austin, in the early 1950's to form the British Motor Corporation Limited brought about rationalization of the numerous facets of their activities and this led to the adoption of common engines for vehicles of similar size marketed under the several marques produced by the group. Three basic engines were ultimately developed for installation in passenger cars and were styled "A", "B" and "C". Two were four-cylinder units of Austin origin, and the largest, the "C" series engine, was a six-cylinder unit evolved from a truck engine design by the Morris engines branch. The "A" and "B" series engines were direct descendants of the Austin A/40 engine which, along with the A/70 and four-cylinder A/90 engines, was related to the 2.2 litre overhead-valve Austin Sixteen power plant. This in turn had been the post-war result of an uncompleted wartime project to produce a replacement engine for the Jeep in England, and bore some relationship to the existing 3 1/2 litre Austin truck motor.

Those unfamiliar with the reputation earned by the first Austin A/40 (not the "Farina" A40) will be surprised to learn that one completed 10,000 miles in 10,000 minutes at Montlherry, France, and closer to home one owned by the late Cec Warren of Victoria covered some 67,000 miles in arduous reliability trials and as towing unit for his racing cars without major overhaul. This was the heritage of the "B" series engine and, although it was intended from the outset that it be a 1 1/2 litre unit, the first examples produced were in fact small bore 1200 c.c. versions installed in some 1953/4 Austin A/40's and later on in the Morris Cowley.

DESIGN AND TECHNICAL INNOVATIONS
Incorporated in the "B" series engine are a number of technical innovations and characteristics not readily revealed by the usual sales information given to the public on brochures and etcetera, and it is these which are the basis of the units success.

They are: - a. an exceptional deep cylinder block/crankcase casting.
                 b. a Weslake designed cylinder head c. a BMC-patented crankshaft journal lubrication system; and
                 d. sine-wave form slanted cam faces.
       Continuation of the crankshaft casting well below the crankshaft centre-line and the use of a short, hefty crankshaft - made possible by the offset con-rods - provide the engine with great rigidity, whilst the patented lubrication system endures longevity of bearing surfaces. This system's special feature is the provision of a two-point oil supply to each bearing, the one at the underside delivering a greater amount of oil as the other includes a restricter. Main bearings receive lubricant from four points. The chain-driven camshaft is made of case-hardened steel and is located at normal height on the block. It operates the valves via pushrods. Correct tension of the duplex roller timing chain is maintained by a spring-loaded shoe - incorporating a synthetic face. It is automatically adjusted and has individual lubrication.

This device is most effective and a considerable advance on that used in the A/40 engine, a rubber ring located between the camshaft gear's two rows of teeth. The sine-wave cam profile reduces valve-spring surge and the slanted cam face causes the tappets to rotate, thus ensuring even wear of their bases. The engine has a high rate of thermal efficiency, which results in economical operation and a good measure of low speed torque. This characteristic stems from the work of Harry Weslake, who planned the "breathing" and combustion control. The Weslake combustion chamber is a heart-shaped affair with the wall protruding deeply between the valves. The spark plug is located at the base of the "heart" and maintenance of the desired turbulence pattern is achieved by using concave-topped pistons.

From this point the several versions of "B" series engine differ in detail, even where cubic capacity is the same. A classic example of this is the difference between the current English and Australian 1622 c.c. engines. B.M.C. Australia initiated development of the 1622 c.c. 3 in. bore engine and its six-cylinder off-shoot, the 2433 c.c. "Blue Streak" engine used in the Freeway and Wolseley 24/80. These two engines were designed with Australian requirements the prime consideration, and thus, when the parent company decided to enlarge its engine to 1622 c.c., a separate pattern of development was followed.

AUSTRALIAN VERSION WITH SIX CYLINDERS
The Australian six-cylinder "B" series engine is virtually a 1622 c.c. four with two more identical cylinders added, thus the cylinder block, cylinder head, crankshaft, camshaft, manifolds, sump and distributor are the only items which differ.

The 1798 c.c. version has been turned east-west for the Austin 1800, and has been given a five bearing crankshaft. This same engine, mounted north-south, powers the MG-B. Of course, it has higher compression and twin SU carbs.

SOURCE: Australian Motor Manuals Auto-Almanac, 1966