The engine block houses all major components that provide power to the engine, mainly the crankshaft, the pistons and often the camshaft.  Dependent on an engine's individual design specifications, specific auxiliary units can be attached to the engine block.

In its dual role, the engine block, also known as the cylinder block, is both an engine casing and cooling jacket, making it the central constituent in an internal combustion engine.

Engine blocks are proportionately substantial and heavy objects, produced as a single part cast in a single part, usually in cast iron and occasionally aluminium for lighter vehicles built for speed.

For larger vehicles, the engine block is often constructed from two matching parts, each bearing its own crankcase cylinders.

Among the various tasks that an engine block performs when the vehicle is in motion are the following:

• Transferring the inertia and fuel  (dynamic) forces of an engine.
• Providing a mounting for the crankshaft drive
• Providing a mounting and connection for the cylinder head.
• Providing a mounting for the crankshaft.
• Providing a mounting for the camshaft (if required).
• Providing appropriate channels to transport coolants and lubricating oil.
• Integrating the crankcase ventilation system
• Providing a connection to  either the transmission or valve control drive
• Mountings for a variety of auxiliary units
• Sealing the crankcase through the oil sump.

When considering purchasing a classic car for restoration, careful attention should be paid to the engine block as repairs will be costly and replacing one can be horrendous.

The engine block is a large piece of metal, solidly built to be enough to last the car's lifetime.

That does not mean that the engine block cannot cause problems. When inspecting the block, time should be taken to find the most minor of cracks and splits.

This is a job that can be more problematic than it seems from the outset, as not all cracks are visible from outside the block.

No matter how minute they appear, these imperfections will eventually spread and cause the engine to fail.

These most common signs of engine block problems include blue or grey smoke pouring out from under the hood, coolant leaking from the engine, persistent overheating or dramatically reduced performance.

The common cause for these problems is if excessive heat is allowed to build up in the block due to coolant levels falling to below the permitted level, especially during extreme weather conditions, or the vehicle carrying too many people or heavier loads than it was designed to bear.

If it appears that the engine block has cracked, then the only option is to have it repaired as well and as inexpensively as possible.

The first and least expensive option is to have the cracks welded with the aid of an arc welder. If this can be done in-house, the savings can be considerable, although these savings should not come at the cost of a sub-standard repair.

Even the most experienced arc welder will be unable to prevent the engine block from losing its original shape, which can have long term effects on the engine's performance.

A more appealing repair option is to send the engine block out to have the crack repaired using a process known as cold metal stitching.  As the name suggests, cold metal stitching is a more localised repair, although it can be susceptible to sudden rises in temperature in the block, usually caused by overheating. 

Engine blocks that have been repaired using cold metal stitching will undoubtedly have a more aesthetic appearance than those which have been arc-welded, although the repair bill will be a lot higher.

Another repair process from the same source is applying cold metal patches over the crack, sealed with either epoxies or powerful adhesives. Applying cold metal patches is a more effortless and less expensive alternative to stitching but is not always guaranteed to offer a long-lasting solution.

If the crack (or cracks) in the engine block are in their infancy and not too large, applying a commercial sealer to the cracks might be a very efficient long term solution at a cost that will not break the bank. 

Commercial sealers are added to the vehicle's cooling system, where they will expand to form a seal between the cracks. 

The costs of repairing a cracked engine block can run from £3000 downwards depending on the nature of the repair and the method used.

What should always be borne in mind is that once an engine block has undergone any form of repair, it can only be regarded as "damaged goods". That means it will always be susceptible to damage in the future, especially if the block is ever allowed to overheat. This means that great care must be taken to ensure that this does not happen.