Heron cylinder head
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
- 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.
- Alfa Romeo Alfasud boxer engine
- Audi F103 pushrod four engine used in different Audi models of the 60s and 70s
- Moto Guzzi
- Moto Morini 3½ & 500
- Ford Essex V4 engine
- Ford Essex V6 engine
- Ford Kent engine
- Jaguar V12 engine
- Puma racing engines
- Rover 2000 P6
- VW EA827 engine (e.g. the 1600cc 100 bhp engine of Audi 80 GT)
- Volkswagen Wasserboxer Vanagon engines
- Volvo 200 B200K 110PS / B230K 117PS
- Volvo 700
- Volvo 900
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