What is an Engine Block?

Mary McMahon
Mary McMahon

The engine block is the linchpin of vehicles that run on internal combustion, providing the powerhouse for the vehicle. It is called a "block" because it is usually a solid cast car part, housing the cylinders and their components inside a cooled and lubricated crankcase. This part is designed to be extremely strong and sturdy, because its failure results in failure of the car, which will not function until the engine block is replaced or repaired.

Four-cylinder engine block.
Four-cylinder engine block.

Most engine blocks are made of cast iron, although in the late 1990s, some made from plastic and other experimental materials were being used in prototype cars with the hope of developing more lightweight, efficient vehicles. A cast iron one can comprise a substantial portion of the weight of the car, and usually requires multiple people to be removed and worked on safely.

Working from the outside in, this part starts with a solid metal outside, designed to seal everything inside. A number of channels and passages inside comprise the cooling jacket and are designed to deliver water from the radiator to all the hot sections of the engine, preventing overheating. After the water is circulated in the engine, it returns to the radiator to be cooled by the fan and sent back through the engine.

The core of the engine block is the cylinders, capped by the cylinder head. The number of cylinders determines the size and placement of the block, with most cars having between four and eight cylinders. These cylinders house pistons, which provide motive energy for the vehicle through a series of controlled explosions inside the cylinders which push the pistons out, moving the crankshaft of the vehicle.

Attached to the bottom is the oil pan, which seals in the lubricating oil for the engine. Periodically, the oil for the car must be changed, and the oil pan is drained and refilled to remove the older oil, which has lost viscosity and picked up impurities.

The engine block is the collective term that refers to the crankcase and all the components that fill it, including gaskets, valves, and seals. Because of its importance in the functioning of the car, drivers should perform regular maintenance on their vehicles to prevent damage to internal parts that can be caused by overheating, insufficient oil, and other easily preventable situations.

During normal operations, the engine block becomes extremely hot, and drivers should be cautious about touching it until it has cooled sufficiently. Some enterprising drivers and aspiring chefs have also experimented with cooking foods such as baked potatoes on the engine, although this is not generally recommended because the food may become dislodged during cooking, potentially causing damage to the engine.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


@ Alchemy- You should have a second opinion done before you pay for a cylinder head replacement, because it could very well only be a blown cylinder head gasket. The cylinder head sits on the block, separated only by the head gasket. A cracked head will spill radiator fluid around the spark plugs, but so can a warped head and a blown gasket. Warped and cracked heads can cost between$ 750-$3000 to repair depending on the parts used, labor costs, and the type of engine. Replacing a gasket will cost much less.

If your car is older, the cylinder head is indeed cracked, and you have no sentimental attachment to the vehicle, you may want to consider looking for an engine for sale. It may be cheaper to replace the engine, and you may find a better engine with fewer miles than the one you currently have.


What is the difference between cylinder heads and an engine block? Are they the same? If I have a cracked head can I just have a cylinder head replacement done, or do I need to replace the entire engine? How much does something like this cost?

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