Monobloc engine
![De Dion-Bouton engine with monobloc cylinder heads, c. 1905[1]](/uploads/202501/28/De_Dion-Bouton_engine_(Rankin_Kennedy,_Modern_Engines,_Vol_III)4859.jpg)
![Napier engine, with monobloc head[2]](/uploads/202501/28/Napier_petrol_boat_engine,_side_section_(Rankin_Kennedy,_Modern_Engines,_Vol_III)4859.jpg)

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A monobloc or en bloc engine is an internal-combustion piston engine where some of the major components (such as cylinder head, cylinder block, or crankcase) are formed, usually by casting, as a single integral unit, rather than being assembled later. This has the advantages of improving mechanical stiffness, and also improving the reliability of the sealing between them.