Engine Blocks and Liners

The primary function of the engine cylinder block described in this ILM is to:

Support only the cylinder head Provide the main structure of the engine, enclosing cylinders and supporting crankshaft and related components Hold only external accessories such as alternators Store engine coolant only

Most traditional engine blocks have been manufactured from:

Plastic Cast iron alloys chosen for strength and wear resistance Glass Pure copper

A growing number of modern blocks are built from aluminum alloys because they:

Are stronger but much heavier than iron Reduce weight and improve heat dissipation when properly designed Cannot be used with liners Eliminate the need for coolant

The ILM states that the cylinder block normally includes:

Only external mounting lugs Cylinders or liners, coolant jackets, oil passages and main bearing supports Only crankshaft and pistons Only valve covers and intake passages

Core (expansion) plugs in a block are used to:

Adjust compression ratio Seal casting core openings and help protect against freeze damage if coolant freezes Lubricate bearings Support valve train components

The deck surface of an engine block is the:

Bottom surface where the oil pan mounts Machined top surface where the cylinder head or heads are bolted on Side surface where accessories attach Surface of the crankshaft journals

In a 'parent bore' block design:

Separate cylinder liners are installed and replaceable Cylinders are machined directly into the block casting with no separate liners No coolant surrounds the cylinders Cylinder sleeves are made of plastic

Dry cylinder liners are described in the ILM as:

In direct contact with coolant on their outer surface Pressed into the block with their outer surface not directly exposed to engine coolant Made of aluminum with no contact to the block Used only in air-cooled engines

Wet cylinder liners differ from dry liners because they:

Do not contact coolant Have their outer surface directly exposed to engine coolant inside the block Cannot be replaced Are made only for small engines

One advantage of wet liners mentioned in the module is that they:

Eliminate coolant leaks completely Allow easy replacement of worn cylinders and can provide good cooling around the liner Require no sealing rings Can only be used in gasoline engines

Cylinder sleeves or liners are often made from materials that:

Are softer than the piston rings Provide hard, wear-resistant surfaces such as alloy cast iron Melt at engine operating temperatures Are transparent

Cross-bolted main bearing caps and bedplate designs are used to:

Reduce block strength Increase rigidity of the lower end and control crankshaft movement under high loads Reduce manufacturing cost only Provide more oil leaks

The ILM notes that many blocks include cast-in coolant jackets that:

Surround only the crankshaft Surround cylinder walls and parts of the head area to carry heat away Contain fuel only Are unused in diesel engines

Main bearing saddles in the block are the:

Upper control arms for suspension Areas that support the upper halves of the crankshaft main bearings Supports for the transmission Mounts for the starter motor only

When replacing an engine block, the ILM emphasizes the need to match:

Paint colour only Correct engine family, casting number, deck height, main bearing size and accessory mounting provisions Only number of cylinders Any similar block regardless of details

Cylinder wear in a parent-bore block is often corrected by:

Painting the block exterior Boring and honing to an oversize and installing matching pistons and rings Adding thicker head gaskets Installing smaller pistons only

Deck cracking between cylinders or coolant jackets can lead to:

Improved cooling Coolant leakage into cylinders or oil and loss of compression Better fuel economy Reduced emissions

Cylinder liner protrusion above the block deck on wet-liner engines must:

Be ignored during service Meet specified values to ensure proper head gasket sealing Always be zero Be as high as possible

Block deck surfaces are checked with:

A tire gauge Straightedges and feeler gauges or specialized measuring equipment for flatness A spark plug tester Only visual inspection from a distance

The ILM reminds parts technicians that replacement blocks and liners often come with:

No documentation Specific installation instructions and dimensional data that must be followed Only shipping paperwork Random accessories not related to the engine

An open-deck block design is characterized by:

Solid material surrounding each cylinder at the deck Large open areas around the cylinders at the deck allowing more coolant flow No coolant passages Separate bolt-on cylinders

A closed-deck block design provides:

Less strength around the cylinders More material around the top of cylinders for strength at high pressures No support for the head gasket Cooling passages only at the bottom

Cylinder numbering patterns and bank identification are important because they:

Are used only by drivers Help with correct diagnosis, firing order and parts ordering Change every time plugs are replaced Apply only to diesel engines

A typical heavy-duty diesel block described in the ILM will:

Have very thin main webs Be robust, often use wet liners and cross-bolted mains for high cylinder pressures Use plastic main caps Have no coolant passages near cylinders

Liner sealing rings (O-rings) on wet liners are used to:

Support crankshaft weight Prevent coolant from leaking into the crankcase at the liner lower end Control oil pressure Adjust piston-to-wall clearance

A 'siamesed cylinder' block design refers to:

Cylinders that share a common bore and piston Cylinder bores cast so close together that there is little or no coolant passage between them Cylinders located in separate blocks Cylinders arranged in a V-shape

From a parts perspective, engine block-related sales opportunities include:

Only crankshafts Blocks, liners, core plugs, main bearing sets, head bolts, gaskets and sealants Only spark plugs Only timing belts

Block damage from freezing coolant most commonly appears as:

Improved paint finish Cracks in outer walls or pushed-out core plugs Shiny cylinder walls Loose piston pins

When ordering replacement liners, the ILM stresses checking:

Only approximate bore size Engine model, liner type (wet/dry), flange design, length and outside diameter dimensions Only engine oil brand Only the vehicle’s odometer reading

In some modern engines, the block and crankcase assembly may incorporate:

No main supports An integrated bedplate or ladder frame that ties the main bearing caps together Only two main bearings Only external ribs for decoration

The ILM indicates that reconditioning operations performed on blocks include:

Painting spark plugs Cleaning, crack detection, boring/honing cylinders and resurfacing decks Replacing tire treads Straightening steering arms

Cylinder taper and out-of-round conditions in a block are checked to determine if:

The engine has enough oil The bores can be used with standard pistons or require oversize service The cooling system is full The starter is operating correctly

Some aluminum blocks use cast-in iron cylinder liners to:

Increase engine noise Provide durable cylinder surfaces while keeping block weight low Prevent coolant circulation Allow the use of plastic pistons

Head bolt threads in the block must be:

Ignored unless stripped Cleaned, inspected and sometimes repaired with inserts according to manufacturer procedures Filled with sealant to prevent torque Painted before installation

Block casting numbers and ID tags are important because they:

Indicate only the paint colour Help identify specific engine families, revisions and correct replacement parts Are decorative only Apply only to gasoline engines

The ILM points out that replacement short blocks:

Include vehicle body panels Typically include a new or remanufactured block, crankshaft, bearings and sometimes pistons/rods Never include any internal parts Replace only the cylinder head

The parts technician must often explain to customers that block and liner replacement decisions depend on:

Only vehicle colour Extent of damage, cost of machining versus replacement, and intended service life of the engine Number of cup holders Air conditioning performance

Coolant passages in the block are designed to:

Lubricate the crankshaft Carry heat away from cylinders and combustion areas to the radiator Store extra oil Increase compression ratio