LO 8-5 Identify and describe the configuration and construction of common cylinder block cylinder arrangements
| Site: | CDX Learning Systems |
| Course: | DE Section 2-1: Engine Blocks and Cylinder Heads |
| Book: | LO 8-5 Identify and describe the configuration and construction of common cylinder block cylinder arrangements |
| Printed by: | Guest user |
| Date: | Thursday, 5 November 2026, 7:44 PM |
1. Cylinder Block Configurations
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
Cylinder Block Configurations
Cylinder blocks can be categorized not only by the cylinder arrangement, construction material, or method of crankcase reinforcement but also by how the cylinders are formed within the block. The cylinders themselves may be integral to the block casting or replaceable liners supported by the block structure. Several configurations for manufacturing cylinder blocks exist to accommodate different engine applications, production costs, rebuild costs, and expected vehicle life cycles. For example, some diesel engines are installed in a chassis or piece of equipment with a relatively short life cycle or operated very few hours over the machine’s life cycle. A delivery truck, operating in an urban environment, or a compact loader will typically use an inexpensive cylinder block generally not intended for rebuilding after 10,000–15,000 hours of operation. Diesels with premium features enabling them to be quickly rebuilt are installed in applications where the vehicle or machine has a high initial purchase cost or long chassis life. Mine trucks, HD off-road equipment, HD farm machines, or on-highway tractors are examples of engines requiring quickly rebuildable cylinder blocks that enable the engine to be returned to service with original specifications. Today, on-highway trucks in this category can easily travel more than 1 million miles (>1,609,344 kilometres [km]) or 30,000 hours of engine operation before requiring an overhaul, when properly maintained. Off-road equipment engines, running at constant speeds, can often operate even longer, to well over 50,000 hours, before rebuilding is necessary. Achieving these operating limits is a function not only of maintenance but also of cylinder block design outlined in the next sections. Common cylinder block construction types include parent bore, wet sleeve, and dry sleeve.
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1.1. Parent Bore Cylinder Blocks
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
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Parent Bore Cylinder Blocks A parent bore cylinder block, also commonly called a no-sleeve block , has holes cast and bored into the block, and the pistons are inserted directly into these holes. No provision is made to add a cylinder sleeve to this type of block. The cylinder walls form a part of the block structure, giving it rigidity and strength Figure 34. The most notable advantage of the parent bore block is that it costs less to construct because machining and fitting of cylinder sleeves is not required. Unlike sleeved blocks, the cylinder walls are structural members of the casting, adding strength and rigidity to the block while requiring less block material. Thin cylinder walls, with minimal material thickness between cylinders, permit compact, lightweight construction. These blocks are best used in applications in which chassis life and expected engine life are approximately equal. Part of the reason for this shorter service life is the relative lack of hardness of cylinder block materials forming the cylinder walls. Cylinder wall surfaces are not as easily hardened as sleeved engines. Without costly alloys and hardening techniques, the cylinder walls will wear at a faster rate than hardened, replaceable cylinder sleeves. Because cylinder walls are irregularly thick, heat transfer differentials create uneven cylinder dimensions and accelerate cylinder wear. Induction hardening of cylinder walls and hardened steel piston rings is one approach used to increase engine durability in parent bore blocks. |
FIGURE 08-34: This 6.7 L (409 in3) Cummins is an example of a parent bore block. A parent bore block forms the cylinders and block from a single casting. Water jackets and other internal passageways are cast into the block. |
FIGURE 08-35: Reboring increases the diameter of a cylinder, which requires a new, oversize piston and ring set to fit the new cylinder dimensions. |
Unlike sleeved engines, wear in a parent bore is offset by the use of coolant jackets formed inside the block that permit cooling of cylinder walls all the way to the top of the block. This feature reduces carbon formation on pistons and other problems related to excess heat near the top of the cylinder. Another major disadvantage of parent bore blocks is what repair or rebuild methods are available when an engine is worn out. If an engine is rebuilt or repaired at the end of its service life, a worn cylinder must be rebored to an oversize dimension or heavily honed. Reboring requires special machining equipment to cut away the worn parts of the cylinder. The cylinder wall is machine cut to remove its worn dimensions, which gives the walls a straightened, uniform diameter from top to bottom Figure 35. After reboring, the cylinder is honed to give it a proper crosshatch finish. An oversize OEM or aftermarket piston must be available to fit into the larger-diameter cylinder. Often only a 0.040" (1.016 mm) oversize is available for a single major rebuilding. An alternative to boring is to use a straight-sided honing stone to grind in a uniform cylinder dimension. This operation is performed only if the cylinder is not excessively worn and a new piston with the correct oversize dimension of 0.010" (0.254 mm) is available. Both honing and reboring are typically done at a metal machine shop. Usually, the engine must be removed from the chassis and completely disassembled to perform the machining processes. The number of times the engine can be rebuilt is limited to available piston oversizes and the thickness of the cylinder walls. What this all means is parent bore blocks are not as durable or rebuildable as sleeved engines. Note, however, that parent bore CGI blocks do not wear as fast as cast iron parent bore blocks. |
| Technicians Tip | ||
| An often-asked question is just how long can an engine last? Particle contamination of an engine is the greatest factor limiting engine service life. Invisible and microscopic-size particles, entering through the air intake or open oil filler caps, are the most destructive (according to numerous research studies performed by Cummins, GM, and others). When experimentally contaminated engines are operated to destruction, it is particles between 5–10 microns (µm) in size that cause more than 3.5 times more wear of piston rings and bearings than large particles. Even smaller particles, between 0-5 µm, cause more than three times more wear than larger particles between 10-20 µm. |
| Technicians Tip | ||
| Coolant temperatures are hotter at the rear of the engine, where coolant must travel the farthest to remove heat. A 10–20° F (−12 to −6.6° C) temperature differential exists between the temperature of coolant near the front of the block and the rear of the block, which is farthest from the radiator. Some engine rebuilders recommend a larger piston-to-cylinder wall clearance in the rearmost cylinders of some V8 diesel engines to allow for greater heat expansion of pistons and cylinder bore diameters. |
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1.2. Sleeved Cylinder Blocks
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
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Sleeved Cylinder Blocks To rapidly restore a worn-out or damaged cylinder to original specifications, replaceable sleeves are used in premium featured diesel cylinder blocks. The replaceable wear surfaces making up the cylinder wall are called sleeves or liners . Constructed to the same inside diameter and length of the cylinder found in a comparable parent bore block, sleeves may be replaced individually if they become worn or prematurely damaged. Cylinder sleeves are typically made from harder alloys (cast iron) than the cylinder block. More often, the sleeve is made from ductile iron, which has its natural silicon content reduced to only 3–4% and the addition of 1–4% manganese metal alloy. The materials change the normally crystalline composition of cast iron to make it more ductile or bendable, which is more resistant to cracking from intermittent mechanical stresses. Good-quality liners are also centrifugally cast, which means the iron is poured into a spinning mold before slowly cooling. This allows impurities to separate from the metal, where they are machined away, and increases the density of the liner material. Finally, a quality liner will be induction hardened to increase its wear resistance. Steel is not used as a liner material because of its much lower carbon-graphite content that makes it less compatible as a wear surface for rings and pistons. Steel, though much tougher than iron, would simply increase cylinder wear of rings and pistons. Sleeves are commonly used in medium- to large-bore engines operating under extended service conditions and high engine hours. Replacing the liner sleeves using cylinder kits, made up of new pistons, rings, and liners, enables rapid restoration of an engine to factory specifications Figure 36. There are several different types of cylinder liners in use. Dry liners are a liner type that has no contact with coolant, hence the name dry sleeve Figure 37. The other major category is wet liners. Several different types of wet liners are used in modern diesel engines and classified depending on where the liner seats or transfers its clamping load in the block and how it seals coolant. The most commonly used wet-type liners are top-stop, full- or bottom-stop, and mid-stop, also called half-stop liners Figure 38. |
FIGURE 08-36: Replaceable cylinder sleeves enable a worn-out engine to be quickly rebuilt and restored to factory specifications. |
FIGURE 08-37: Various types of cylinder sleeves. |
FIGURE 08-38: Note three common liner designs. Names are given to the liner category according to what area of the liner is used to seat it in the block, either at the top, middle, or bottom. |
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1.3. Video: Cylinder Sleeve Types
LO 8-05 Video: Cylinder Sleeve Types |
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1.4. Dry Sleeve Blocks
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
Dry Sleeve Blocks
A dry sleeve cylinder block is designed with a bored or honed hole in the block that allows no coolant contact with the cylinder sleeve. The sleeve is inserted into the bored hole as either a slip or an interference-type, pressed-in fit. If the liner is installed with an interference fit, meaning the liner is slightly larger than the cylinder bore, it does not usually have a top flange, but it is machined flush with the block deck. A slip-fit liner will use a counterbore machined into the block to accommodate the liner flange, and the flange locates or seats the liner into the block. These liners are usually lubricated externally with engine oil to ease installation Figure 39. Pressure, applied by the cylinder head to a slight protrusion of the liner flange, will prevent liner movement.
FIGURE 08-39: Comparing dry and wet liners. |
Aluminum blocks will use hardened iron alloy sleeves, which are cast in place and not removable. To replace these sleeves, the liner is cut out of the block with a machine tool and a new one is pressed in place. In other blocks with field replaceable dry sleeves, the dry sleeve’s advantage is the absence of contact with coolant that could cause sleeve corrosion. Additionally, the absence of coolant contact means there is not a requirement to seal the sleeve with O-rings or special sealing surfaces to prevent coolant leakage into the crankcase. Cylinder sleeves may be replaced individually if they become prematurely worn or damaged.
Dry sleeves have some disadvantages. Because the coolant is not in direct contact with the dry sleeve, heat transfer from the combustion chamber to the liquid coolant is not as rapid as it would be with a wet sleeve. This slow heat transfer may potentially result in limitations on power output per cylinder, shortened engine life, and cylinder damage. Extra steps in manufacturing and machining the block are required for sleeve installation. Dry-sleeved blocks tend to weigh more than parent bore blocks.
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1.5. Wet Sleeve Blocks
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
Wet Sleeve Blocks
A wet sleeve block is designed with a number of large holes or cavities into which the cylinder sleeves are inserted. Wet sleeves are made from alloyed ductile iron that is centrifugally cast and induction hardened. The walls of these liners are thick and strong enough to withstand the heat loads and combustion forces in high horsepower engines that may appear to be better handled by a parent bore block Figure 40. Coolant has direct contact with the outside of the sleeve, and there is no mechanical support like a dry sleeve has with its surrounding block. Machined surfaces inside the block structure provide points to clamp, locate, and center the wet liner in the block. Depending on the type of wet liner, O-rings, crevice seals, or a combination of room temperature vulcanizing (RTV) silicone and narrow metal-to-metal contact points are used to seal leakage from block passages circulating coolant around the liner Figure 41. O-rings prevent coolant leakage from the water jackets and into the oil pan in blocks with top- and bottom-stop–type liners.
FIGURE 08-40: Nomenclature for a top-stop–type liner that has a sealing flange at the top of the sleeve. |
FIGURE 08-41: A crevice seal near the top of this flangeless mid-stop liner seals coolant from leaking onto the block deck. Silicone seals the lower pilot pad surface. |
The major advantage of wet sleeve liners is the direct contact of coolant with the sleeve, which enables rapid heat transfer from the cylinder to the coolant. One or two machined reliefs on the outside surface may help remove heat from near the top piston ring to prevent carbon buildup on the upper third of the liner. Worn or damaged sleeves are easily removed, and new ones are installed during engine rebuilding to restore the cylinders to original specifications.
Three types of wet liners commonly used today are mid-stop, bottom-stop, and top-stop sleeves. Top-stop liners are the older, more traditional type of sleeve with a flange at the top that locates, centres, and is used to transmit clamping force to the liner in the cylinder block when the cylinder head is placed over the top of the liner. Mid-stop and full-stop liners are a more recent innovation, both showing up in the 1980s to solve common problems with top-stop liners. Mid-stop liners are used in new lighter-weight block designs while heavier full- or bottom-stop liners are used in high horsepower HD engines, which require the longest, trouble-free service and best sealing performance to prevent coolant leaks.
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The major disadvantages of wet sleeve liners are the problems associated with preventing internal engine coolant leaks. The O-ring seal (if used) at the lower part of the liner barrel can deteriorate and leak coolant into the lubrication oil. Some engines have an external weep hole to drain the coolant that has leaked past O-rings and prevent it from entering the oil pan Figure 42. Liner vibration, caused by combustion forces, can amplify the effects of cavitation erosion, which is the perforation of the cylinder or liner wall. Cavitation produces pinholes that can completely perforate the sleeve, allowing coolant to enter the cylinder or combustion gases to enter and pressurize the cooling system. Greater attention to maintenance of the cooling system is required in wet sleeve engines to prevent cavitation. Another problem with using replaceable sleeves is ensuring that liner protrusion above the block deck is within specification and even across all cylinders. All liners require some protrusion to allow the cylinder head to transmit clamping force to the liner when in place, but without correct protrusion, combustion gases will leak past the top of the liner and into the coolant. Because the cylinder head cannot properly squeeze the head gasket if liner protrusions are incorrect, the head gaskets will also leak. Insufficient liner protrusion can allow poorly clamped liners to move. Too much cylinder head clamping force on a liner with excessive protrusion can warp the cylinder head and result in a cracked liner, cracked liner counterbores, or cracked cylinder head. |
FIGURE 08-42: Detroit Series 60 engines have weep holes to drain coolant that may leak past damaged liner O-rings to the outside of the block. The weep hole prevents coolant from entering the oil pan. |
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1.6. Top-Stop Liners
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
Top-Stop Liners
Top-stop liners refer to a liner style that generally uses a heavy flange at the top of the liner Figure 43. This flange is located and centered in a precisely machined ledge recessed in the block deck. When the liner is installed in the cylinder cavity, the head gasket is positioned to sit on the edge of the flange in an area called the crimping bead Figure 44. The head gasket’s metal fire ring, combined with the flange fire dam, will seal the cylinder to prevent leakage of combustion gases into the coolant or across the block deck and down a passageway into the crankcase of the engine. When the cylinder head is tightened, the clamping force of the head is applied to the liner through the head gasket to tightly compress the liner into the counterbore Figure 45. A narrow bead of silicone is often used to help seal below the flange surface to prevent pressurized coolant from pushing around the flange to the counterbore surface. An interference fit either between the top of the flange and the block deck, or the liner area just below the flange and the block, helps seal the coolant from leaking around the liner and onto the block deck. The lower barrel of the liner typically uses a series of O-rings between the liner and the block to prevent coolant in cooling jackets (surrounding the liner) from leaking into the crankcase. Counterbores and liner O-rings are prone to leakage due to O-ring seal deterioration, liner movement, counterbore cracking, wear, and other defects of the counterbore.
FIGURE 08-43: Wet liners have a flange that sits in the cylinder block counterbore. Liner protrusion is needed to hold the liner in place and prevent it from moving. |
FIGURE 08-44: Note the details of the position for the fire ring, fire dam, and liner. The metal fire ring in the head gasket helps seal compression and combustion gases in the cylinder. |
FIGURE 08-45: The details of the arrangement of the head gasket, fire ring, and fire dam to seal the cylinder. |
One major problem with top-stop liners is damage to the counterbore and liner flange due to the high clamping pressures of the head against the flange and the radial loads in the counterbore caused by high-temperature heating of the tightly clamped flange Figure 46. Flange cracks and breaks are also caused by excessive liner protrusion in one cylinder or uneven counterbore ledges. To reduce radial pressure in the counterbore, top-stop liners will often relocate the point where the flange is centered and is press fit to a location on the liner barrel, just below the top flange Figure 47.
FIGURE 08-46: Excessive pressure on the top-stop liner flange will cause a circumferential crack in the flange that can be very hard to detect. |
FIGURE 08-47: The top-stop liner is located and centered either in the counterbore of the block deck or in an area below the counterbore to reduce counterbore damage caused by high-temperature radial loads. |
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1.7. Full-Stop Liners
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
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Full-Stop Liners
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FIGURE 08-48: Note the top flange and lower pilot stop of this full-stop or bottom-stop liner. |
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1.8. Mid-Stop Liners
LO 8-05: Identify and describe the configuration and construction of common cylinder block cylinder arrangements. |
Mid-Stop Liners
To eliminate the problems with the traditional top-stop liner flange, another liner design has emerged called a mid-stop , half-stop , or wet-dry liner (due to its appearance).
Mid-stop liners do not have a flange at the top of the liner that fits into a ledge near the block deck. Instead, a counterbore ledge is approximately halfway (or midway) down the liner Figure 49. In this area, on the ledge sits the equivalent of the liner flange, called a pilot pad . The area in which the pilot is positioned is much stronger than the block deck because it is surrounded by a larger, more rigid block structure. In fact, pilot surface and ledge breakage of a mid-stop liner is unheard of, and expansion of the pilots will not crack the block like tight and hot flanges can cause to block deck counterbores used by top-stop upper press fit liners.
FIGURE 08-49: Mid-stop liners use a steplike pilot near the liner midpoint. Instead of a top-stop flange, the liner has a pilot ledge that seals coolant in the water jacket and locates the liner in the block. |
FIGURE 08-50: Mid-stop ledges and all liner counterbore surfaces need to be carefully inspected for erosion and other damage that creates coolant leak paths. |
Using a mid-stop ledge also eliminates the need for O-rings to seal coolant around the liner. While a rubberlike backup seal may be used on some liner designs, more often only a bead of silicone is used to prevent leakage around the liner pilots and ledge Figure 50. Mid-stop liners can minimize engine block weight by reducing the size of coolant jackets. A narrower, single-wall cylinder block is used around the lower two-thirds of the liner because only the hotter upper third is cooled by coolant jackets. The absence of a top flange also reduces the space required, allowing the block to be made a bit shorter overall.
While every advantage seems to be there for mid-stop liners, top-stop liners have the advantage of having less distortion when installed in the block because they do not squeeze the liner in the middle like mid-stops do.
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