The V-8 engine makes it possible to have a displacement of more that 7 liters in the petrol-engined motor car. It combines a great deal of torque with adequate, smooth running performance, particularly at low RPMs. Altogether however, the construction set-up of the engine is still relatively simple and compact.
Basically, two four-cylinder in-line engines are joined to each other by a single crankshaft at an angle of 90°. However, in most standard V-8s, the crank-journals are not identically positioned. Have a look at the enlargement of picture 2. The connecting-rods of the two opposing pistons are mounted on the same crank-pin. The strokes all overlap by 90°, whereby the cylinders of different sides (banks) always work together. All the moving parts of the crank mechanism, except the crankshaft itself and possibly the complete cylinder heads, can be taken over from the four cylinder.
The firing order is normally 1 5 4 8 6 3 7 2. Variations are found in the racing sector, where the angle between the adjacecent lying journals can be 180°, all on one level.
Modern eight-cylinder engines don't always have an angle of 90° between the cylinder-banks, sometimes, e.g., they have 72°, to reduce the width of the engine. In this case, each connecting rod has it's own crank-pin.
The eight-cylinder shown in picture 1 is actually typical of North America at a time, when the price of fuel did not even play a part. This is a so-called 'pushrod-engine' because in contrast to the OHC engines, the camshaft, which does the work through rocker-arms and pushrods is low-lying in the engine-block. The intake air reaches the inlet manifold through a four-barrel carburettor. The side-valve engine in picture 3 is even older, it comes from a Ford truck. This model still runs on petrol, it has a displacement of 3,6 liters and produces 66 kW (90 hp) at 4000 RPM. 09/11