Heron cylinder head

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A Heron cylinder head, or simply Heron head, is a design for the combustion chambers of the cylinder head on an internal combustion piston engine. The head is machined flat, with recesses only for inlet and exhaust valves, spark plugs, injectors and so on. The combustion chamber itself is contained within a dished depression in the top of the piston. The Heron head is suitable for petrol and diesel engines, for ohv and ohc valve-gear, and for small and large engine displacement capacities.

A flat cylinder head can be combined with simple flat-top pistons, but that choice ignores the reasons for having a depression in the top of each piston, namely: (i) it provides a compact space for combustion to begin, allowing an optimal flame front; and (ii) it creates significant "squish" as the piston reaches TDC. This causes turbulence, which is desirable because it promotes more extensive mixing of the fuel/air mixture: cf: cf1, cf2, cf3).

Pros & Cons[edit]

  • Advantages include: simplicity of manufacture; compact dimensions; accuracy of the flat machined surface; simplified valve-gear; efficient combustion with good fuel economy.
  • Disadvantages include: the greater size and weight of each piston; volumetric efficiency poorer than conventional cylinder heads.


Chevrolet 348-409 V8 engines, 1958-1965

Ford 383-410-430-462 "MEL" V-8 engines, 1958-1968

Ford 401-477-534 "Super Duty" V-8 engines, 1957-1982