Midland Cylinder Heads

Please view the above video it contains lots of useful information on how to refit a Cylinder Head correctly.

The cylinder head From Wikipedia, the free encyclopedia.

On the internal combustion engine, the cylinder head (often informally abbreviated to just head) sits above the cylinders on top of the cylinder block. It consists of a platform containing the poppet valves, spark plugs and usually part of the combustion chamber. 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 through a convoluted path, which limits the ability of the engine to perform at higher revolutions per minute (rpm), leading to the adoption of the overhead valve (OHV) head design, and the subsequent overhead camshaft (OHC) design.

Internally, the cylinder head has passages called ports or tracts for the fuel/air mixture to travel to the inlet valves from the intake manifold, for exhaust gasses to travel from the exhaust valves to the exhaust manifold. In a water-cooled engine, the cylinder head also contains integral ducts and passages for the engines’ coolant – usually a mixture of water and antifreeze – to facilitate the transfer of excess heat away from the head, and therefore the engine in general. In the overhead valve (OHV) design, the cylinder head contains the poppet valves and the spark plugs, along with tracts or ‘ports’ for the inlet and exhaust gases. The operation of the valves is initiated by the engines camshaft, which is sited within the cylinder block, and its moment of operation is transmitted to the valves pushrods, and then rocker arms mounted on a rocker shaft – the rocker arms and shaft also being located within the cylinder head. In the overhead camshaft (OHC) design, the cylinder head contains the valves, spark plugs and inlet/exhaust tracts just like the OHV engine, but the camshaft is now also contained within the cylinder head. The camshaft may be seated centrally between each offset row of inlet and exhaust valves, and still also utilizing rocker arms (but without any pushrods), or the camshaft may be seated directly above the valves eliminating the rocker arms and utilizing ‘bucket’ tapets. The number of cylinder heads in an engine is a function of the engine configuration. An inline or straight engine has only one cylinder head. A V engine (or Vee engine) usually has two cylinder heads, one for each cylinder bank of the ‘V’. However, Volkswagen Group, for instance, produces a specific type of compact narrow angle V engine called the VR6 engine, where the angle between the cylinder banks is so narrow that it utilises a single head. A flat engine (basically a V engine, where the angle between the cylinder banks is now 180 degrees) has two heads. Most radial engines have one head for each cylinder, although this is usually of monobloc form, where the head is made as an integral part of the cylinder and cannot be removed. Some engines, particularly medium- and large-capacity diesel engines built for industrial, power generation and traction purposes (trucks, locomotives, heavy equipment etc.) have individual cylinder heads for each cylinder. This reduces repair costs as a single failed head on a single cylinder can be changed instead of a larger, much more expensive unit fitting all the cylinders. Such a design also allows engine manufacturers to easily produce a ‘family’ of engines of different layouts and/or cylinder numbers without requiring new cylinder head designs. The design of the cylinder head is key to the performance and efficiency 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.

More Useful Information On Cylinder Heads

The cylinder head is a crucial part of all combustion engines, and cylinder head cracking can result in catastrophic damage to the engine. In some cases, cylinder head cracking may result in such severe injury to the engine that it must be replaced. As a result, most motorists try to prevent cylinder head cracking, as an ounce of prevention in this case is worth many pounds of cure. The causes of cylinder head cracking are all relatively simple and easy to prevent, except in the case of mechanical parts failure through no fault of the operator. The cylinder head, used in combination with a head gasket, seals the cylinders of the car, along with other parts associated with them. The cylinder head is customized for the vehicle, and has very precisely milled surfaces to provide a smooth and flush fit with all connecting parts. In the case of a minor crack, the cylinders may lose compression and misfire. Major cracks can cause severe damage to the cylinders of the engine. For this reason, when replacing either the cylinder head or the head gasket, make sure that you are using the correct parts, including bolts, for the job. Even a brand new car can experience cylinder head cracking if parts have been installed incorrectly or if there are weaknesses in the metal. Especially in the case of a vehicle which is still under warranty, drivers should contest the cylinder head cracking with the dealer. Be certain to inspect any vehicle before you purchase to check for signs of coolant leakage indicating weak spots in the metal or incorrectly installed components. This includes the cylinder head gasket, because improper installation of this vital part can cause cylinder head cracking. Cylinder head cracking has become more common as car manufacturers use mixed metals in their engines. Many vehicles, for example, have a solid cast iron engine block but an aluminium cylinder head. These two metals expand at different rates, and this can lead to cylinder head cracking and head failure. The most common cause of cylinder head cracking is overheating. When a vehicle overheats, it puts stress on all of its metal components, including the cylinder head, which is often at the centre of the heat. This can cause the head gasket to fail, which may lead to cylinder head cracking as the components warp and pressure begins to leak. All drivers should properly maintain their vehicles to prevent overheating. Many drivers mistakenly pour cool water into the radiator when their vehicles overheat, in an attempt to bring the temperature down. This is not a good idea, because the rapid temperature change will cause cylinder head cracking due to thermal stress. In a case where the cylinder head survives overheating, the driver may inadvertently destroy it by trying to do good. To prevent overheating, make sure that your radiator is filled with coolant and in good condition, with a tightly sealed cap. Check to be certain that your engine thermostat is in good working order, and accurately reflecting the temperature. Make sure that you have no leaking or stretched hoses, and that the fan is working effectively. If your car does overheat, stop, turn off the engine, and allow it to cool completely before adding water. Do not mix different brands of coolant. Cylinder head cracking can also be caused by localized hot spots in the engine, which usually represent a failure in some portion of the cooling system.Hot spots are often caused by uneven expansion of engine parts, leaky hoses, and pre-ignition in the cylinders of the engine. If your car has overheated, check the cylinder head and gasket for signs of cracking or warping. If the cylinder head has warped even slightly out a flush state, it will cause cylinder head cracking. In this case, the head gasket may need to be replaced and the cylinder head should be ground even again before it cracks.

Midland Cylinder Head FAQ