Cylinder Head

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In an internal combustion engine , the cylinder head sits on top of the cylinders and consists of a platform containing part of the combustion chamber and the location of the valves and spark plugs . In a flathead engine , the mechanical parts of the valve train are all contained within the block, and the head is essentially a flat plate of metal bolted to the top of the cylinder bank with a head gasket in between; this simplicity leads to ease of manufacture and repair, and accounts for the flathead engine's early success in production automobiles and continued success in small engines, such as lawnmowers. This design, however, requires the incoming air to flow in an upward path,rather than downward which limits the ability of the engine to perform at higher rpm , leading to the adoption of the overhead valve head design engine.

In the overhead valve type engine, the valves are contained in thh cylinder head. Traditionally this type of engine (also known as a push rod engine) used a camshaft and lifters which were contained in the cylinder block portion of the engine and timed in relation to the cranshaft with a timing chain and gear which turned the camshaft 1 time to every 2 rotations of the crankshaft. The camsahft in turn will push up a lifter which in turn pushes up the pushrod which operates the rocker arm opening and closing the valve.

In an over head cam style engine the cylinder head contains the camshaft and the valves, this style engine eliminates the need for pushrods to connect the rocker arm to the lifter.There are many differnet combinations for the over head cam design cylinder head, some use lifers and rockers, while others are a solid type design that actually uses a valve lash setting to adjust the valves and the rocker operates directly from the camshaft to the valve.

Internally the cylinder head has passages called ports for the fuel/air mixture to travel to the intake valves from the intake manifold, and a port for the exhaust gases to travel from the combustion chamber past the exhaust valves to the exhaust manifold.

Most over head valve engines are basically hollow on the inside provides a space for the coolant of the engine to flow in order to remove the heat absorbed into the cylinder head from the combustion process in the engine.

The number of cylinder heads in an engine is a function of the engine configuration . A straight 4 or 6 cylinder engine has only one cylinder head. A V6 or V8 engine usually has two cylinder heads, one on each side of the V, although Volkswagen , for instance, produces a V6 called the VR6 , where the angle between the cylinder banks is so narrow that it utilizes a single head and the combustion chamber actually utilizes part of the cylinder simular to the original 409 chevrolet and 430 lincoln type engines. A boxer engine has two heads.

The cylinder head is key to the performance of the internal combustion engine, as the shape of the combustion chamber, inlet passages and ports (and to a lesser extent the exhaust) determines a major portion of the volumetric efficiency and compression ratio of the engine.

The cylinder head is the single most inmportant decision you will make when building your performance engine. To big or even worse not big enough can drastically change the the actual performance ranges of your engine.To make sure you are getting the proper set up for your engine we reccomend calling one of our performance engine technicians here at RPM Machine. 1-888-732-1595

Written by
Daymon Stephens