A car engine block, commonly known as a cylinder block, acts as a structural framework or housing for all the essential components required for combustion.

To elaborate, the engine block is the main housing, which accommodates all the essential components including (pistons, cylinder heads, camshafts, valves, crankshafts, oil galleries and coolant passages) in modern engines.

As the engine block is the core component for any vehicle, it is designed for durability to tolerate high-temperature pressure. If the engine block is damaged, you are more likely to replace it since repairing can be a tough feat. However, if the damage is minimal, you can attempt to fix it through welding and sealant application.

FUNCTIONAL REQUIREMENT FOR AN ENGINE BLOCK

Engine block is one of the essential parts of the engine. As the engine combustion occurs inside the engine block, it has to sustain a high pressure and temperature environment. Hence, apart from durability and wear resistance, an engine block should be able to withstand vibrations as well.

Let’s take a look at some of the functional requirements for an engine block, including:

• High fatigue strength
• High modulus of elasticity (ease of machining)
• Corrosion resistant
• Low thermal expansion
• High thermal conductivity
• Low density

MATERIAL FOR ENGINE BLOCK CASTING

Based on the functional requirement of the engine block, cast iron or aluminium alloy are often selected to cast engine blocks. The difference between the two depends on the application.

IRON VS ALUMINUM

Whether the engine block is cast with iron or aluminium, each has its perks and drawbacks.

ADVANTAGES OF CAST IRON

• Cheaper
• Higher strength
• Lesser vibrations
• Resistant to warping

DISADVANTAGES OF CAST IRON

• Heavier

ADVANTAGES OF ALUMINUM

• Lighter
• Easy to machine and repair
• Better fuel efficiency

DISADVANTAGES OF ALUMINUM

• Expensive
• Prone to warping

HOW AN ENGINE BLOCK IS MADE

The most common and widely used method for manufacturing engine blocks is sand casting. In the case of aluminium, sometimes die casting is also used.

The sand casting uses sand moulds made from a combination of sand and binders to maintain the mould cavities. Sand moulds are cheaper to produce and can only be used once per casting.

The mould is divided into segments so patterns can be inserted to form cavities. The pattern is usually made of wood, metal or polymeric material. Special care is taken in creating patterns to maintain dimension tolerance as the metal will contract after solidification.

After removing the pattern, the mould cavity is filled with molten metal and allowed to cool. Once the metal solidifies, the sand mould is broken down to prepare the casted product or engine block for machining.

MACHINING

The casted engine block is vibrated to remove excess sand. The casted block is then machined to achieve the required dimensions and smooth out the surfaces.

POSSIBLE CASTING DEFECTS

In engine block manufacturing process, casting is prone to defects if proper care is not taken. If the casted engine block has unwanted defects or irregularities, take a look at some possible casting defects to identify the cause:

• Blowholes –due to entrapped gasses during solidification
• Shrinkage cavity – due to contraction of metal on solidification in an uncontrolled environment
• Mismatched – due to misalignment of sand mould sections (upper and lower)
• Metal penetration – due to large sand grain size as metal fuses into the sand and solidifies

These are just a few defects from a list of many, which can be rectified by taking proper casting and moulding measures. For instance, blowholes can be avoided through adequate ventilation in the mould whereas using small grain sand will prevent metal penetration.

WHAT MATERIAL IS USED TO MAKE ENGINE BLOCKS

The engine blocks are usually made of grey cast iron or aluminium alloys. Both materials offer good fluidity in a molten state for casting and thermal conductivity to resist damage due to thermal shocks. Where cast iron is popular for its strength and less production cost, aluminium alloys can significantly cut down the weight by up to 50%.

The casting of engine blocks requires precision, research and engineering. Quality control ensures the right composition of raw materials is used and proper production procedure is applied for successful casting. Non-destructive testing (NDT) techniques are often employed to check for inner defects.