Cylinder Block - Cylinder Blocks and Crankcase Integrated

Cylinder Blocks and Crankcase Integrated

Casting technology at the dawn of the internal combustion engine could reliably cast either large castings, or castings with complex internal cores to allow for water jackets, but not both simultaneously. Most early engines, particularly those with more than four cylinders, had their cylinders cast as pairs or triplets of cylinders, then bolted to a single crankcase.

As casting techniques improved, an entire cylinder block of 4, 6, or 8 cylinders could be cast as one. This was a simpler construction, thus less expensive (unit-wise) to make. For straight engines, this meant that one engine block could now comprise all the cylinders plus the crankcase. Monobloc straight fours, uncommon when the Ford Model T was introduced with one in 1908, became common during the next decade, and monobloc straight sixes followed soon after. By the mid-1920s, both were common, and the straight sixes of General Motors (along with other features that differentiated GM's various makes and models from the Model T) were prying market share away from Ford. (These were all flathead designs.) During that decade, V engines retained a separate block casting for each cylinder bank, with both bolted onto a common crankcase (itself a separate casting). For economy, some engines were designed to use identical castings for each bank, left and right. The complex ducting required for intake and exhaust was too complicated to allow the integration of the banks, except on a few rare engines, such as the Lancia 22½° narrow-angle V12 of 1919, that did manage to use a single block casting for both banks. The hurdles of integrating the banks of the V for common, affordable cars were first overcome by the Ford Motor Company with its Ford flathead V-8, introduced in 1932, which was the first V-8 with a single engine block casting, putting an affordable V-8 into an affordable car for the first time.

The communal water jacket of monobloc designs permitted closer spacing between cylinders. The monobloc design also improved the mechanical stiffness of the engine against bending and the increasingly important torsional twist, as cylinder numbers, engine lengths, and power ratings increased.

Most engines made today, except some unusual V or radial engines, are a monobloc of crankcase and all cylinders. In such cases, the skirts of the cylinder banks form a crankcase area of sorts, which is still often called a crankcase despite no longer being a discrete part.