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Flathead engine

A crossflow T-head sidevalve engine
The usual L-head arrangement
Pop-up pistons may be used to increase compression ratio
Flathead with Ricardo's turbulent head

A flathead engine, also known as a sidevalve engine[1][2] or valve-in-block engine, is an internal combustion engine with its poppet valves contained within the engine block, instead of in the cylinder head, as in an overhead valve engine.

Flatheads were widely used internationally by automobile manufacturers from the late 1890s until the mid-1960s[3] but were replaced by more efficient overhead valve and overhead camshaft engines. They are currently experiencing a revival in low-revving aero-engines such as the D-Motor.[4]

  1. ^ American Rodder, 6/94, pp.45 & 93.
  2. ^ (As the cylinder cross-section has the shape of an inverted L, other names such as "L-block" or "L-head" are also used)
  3. ^ "What Was the Final Year for a New Flathead-Powered American Car?". 20 December 2018.
  4. ^ "D-Motor image". Archived from the original on 25 February 2018. Retrieved 29 April 2018.

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