Editing BMC B-series engine (section)

==Construction==

The engine was of conventional construction with a one-piece [[crankcase]] and [[cylinder block]] in cast iron with the crankcase extending down to the lowest level of the [[main bearing]] caps; with a [[cylinder head]], also usually in [[cast iron]], and a [[sump]] made from pressed [[steel]] for rear-wheel drive vehicles. Early engines used a three-[[Bearing (mechanical)|bearing]] [[crankshaft]], but later engines used five bearings. On all except the rare twin overhead [[camshaft]] variant, the camshaft — which was chain driven and mounted low in the block — operated the overhead valves via [[pushrod]]s and [[rocker arm]]s. The two inlet ports in the [[Reverse-flow cylinder head|non-crossflow cylinder head]] were shared between cylinders 1 + 2 and 3 + 4 and the three [[exhaust port]]s between cylinder 1, 2 + 3 and 4. [[Valve]] clearance was adjustable by screws and locknuts on the rocker arms.<ref>Austin Motor Company. ''Austin A40 Models Service Manual''. Austin, Birmingham, UK.</ref> Another unconventional characteristic of the engine is that the bore spacing is not constant between all four bores. The distance from cylinder 1 to 2 is 3.4375"; 2 to 3 =3.875"; and 3 to 4 =3.4375".

The B series shares many design features (such as the heart-shaped [[combustion chamber]]s and siamese inlet ports designed by [[Weslake|Harry Weslake]]), as well as its basic layout and general appearance, with the smaller [[BMC A-series engine]]. However another difference was its block's full-depth skirt which provided excellent bottom-end strength. This made the engine highly durable and suitable for developing into diesel versions in later years.