Interesting facts about the cylinder head

by Matthias Bartel
Interesting facts about the cylinder head
Most drivers know what a cylinder head is. At least it is known that it closes off the combustion chambers of the engine at the top. However, this engine part is much more than just a cover. It has a wealth of tasks to perform and is a marvel of engineering.

Layout and function

The engine is actually closed off at the top by a cover, commonly referred to as a valve cover, and sealed with a simple rubber gasket. Below that is the actual cylinder head. It is traversed by channels and bores for the oil to lubricate the valve gear and for the coolant. Other channels are used for gas exchange, the corresponding intake manifold and the exhaust manifold are flanged to the head. Towards the combustion chambers, the openings for the valves are often more than the usual two per cylinder. In the petrol engine there is a threaded hole for the spark plug, in the diesel there are holes for the injection nozzle and glow plug. As if that weren't enough, a camshaft still needs to be mounted in the head.
Of course, this is just a simple description of a cylinder head, there are air-cooled engines, petrol engines with injectors, engines with more than one camshaft or those where the camshaft is housed in the crankcase - the heads look different accordingly.

This highly complex component is exposed to extreme conditions. After a frosty winter night, the engine is brought up to operating temperature in a short time, but everything has to be tight and stay tight - even with the enormously high pressure that prevails in the combustion chamber. For this, the head is manufactured with the highest precision and must be assembled with great care. The cylinder head bolts (stretch bolts) must be tightened in a prescribed sequence, gradually with an exact tightening torque. The material from which the bolts are made must have a certain elasticity so that the head lies 100% flat and with the necessary pressure on the engine block.

Damage can of course occur to this important component, mostly caused by carelessness. Deposits and hairline cracks are caused by overheating as a result of heavy loads or when the engine is operated with the wrong or no coolant. Torn threads and broken studs can ruin the head. Natural wear and tear with high mileage also plays a role, e.g. B. on the valve seats or valve guides.
This is serious engine damage, but fortunately the entire engine does not have to be scrapped in this case. Cylinder heads are available as spare parts for all kinds of engines. A new cylinder head, professionally installed, can completely restore your engine.

• Wikipedia
• Diesel engine (learning commercial vehicle technology) by Michael Hilgers
• Gasoline and diesel engines from Grohe and Russ

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