Editing Straight-six engine (section)

=== Crankshaft ===
[[File:I6crankandblock.jpg|thumb|Crankshaft with four main bearings]]
[[Crankshaft]]s for straight-six engines usually have either four [[main bearing]]s (i.e., a bearing in between each pair of [[crankpin]]s and one at each end) or seven main bearings (i.e., a bearing between every crankpin):
* Large displacement and diesel engines typically use seven bearings to minimize crankshaft flex. When an engine is subject to high loads at low speeds, the greater distance between main bearings causes increased crankshaft flex. Modern high-compression engines subject the crankshaft to greater bending loads from higher peak gas pressures, requiring the crank throws to have more significant support from adjacent bearings. So, it is common for straight-six engines to use seven main bearings.<ref name="Nunney"/>{{refpage|p38}}
* Smaller and high-performance engines{{when|date=September 2022}} typically use four bearings since having fewer main journals decreases friction and increases the torsional stiffness of the crankshaft. The lack of torsional stiffness can make the seven main bearing designs susceptible to torsional flex and potential breakage at high engine speeds. Any torsional flex in the crankshaft is compounded by the torsional flex of the [[camshaft]]s for the rear cylinders since the camshafts are rather long and subject to torsional flex. At high engine speeds, the combination of camshaft and crankshaft flex results in inaccurate timing of the valve openings, which, in the worst case, can cause the valves and pistons to collide with catastrophic results.