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Bore pitch is the distance between the centerline of a cylinder bore to the centerline of the next cylinder bore adjacent to it in an internal combustion engine. It's also referred to as the "mean cylinder width", "bore spacing", "bore center distance" and "cylinder spacing".
The bore pitch is always larger than the inside diameter of the cylinder since it includes the thickness of both cylinder walls and any water passage separating them. This is one of the first dimensions required when developing a new engine, since it limits maximum cylinder size , and determines the length of the engine or of that bank of cylinders.
In addition, the positions of the main bearings must be between individual cylinders , or between adjacent pairs of cylinders.
In some older engines the bore pitch is additionally extended to allow more material between the main bearing webs in the block. For example, in an L6 the first pair , center pair , and rear pair of cylinders that share a pair of main bearings have a smaller pitch than between #2 & 3 and #4 & 5 that "bridge" a main bearing.