Editing Flathead engine (section)

==Advantages==
The advantages of a sidevalve engine include: simplicity, reliability, low part count, low cost, low weight, compactness, responsive low-speed power, low mechanical engine noise, and insensitivity to low-octane fuel. The absence of a complicated valvetrain allows a compact engine that is cheap to manufacture, since the cylinder head may be little more than a simple metal casting. These advantages explain why side valve engines were used for [[car|passenger cars]] for many years, while [[Overhead valve engine|OHV]] designs came to be specified only for high-performance applications such as [[aircraft]], [[luxury car]]s, [[sports car]]s, and some [[sport motorcycle|motorcycles]].{{citation needed|date=October 2021}}

At top dead centre, the piston gets very close to the flat portion of the cylinder head above, and the resultant [[Squish (piston engine)|squish]] [[turbulence]] produces excellent fuel/air mixing. A feature of the sidevalve design (particularly beneficial for an aero-engine) is that if a valve should seize in its guide and remain partially open, the piston would not be damaged, and the engine would continue operating safely on its other cylinders.{{citation needed|date=October 2021}}