Engine basics

Bedplate Design Blocks

A bedplate is a structural member that attaches to the bottom of the block and supports the crank-shaft. Under the bedplate is the oil pan, which in mos tcases is also part of the structure and support for the block assembly

what is a cross drilled crankshaft

A cross-drilled crankshaft means that there are two instead of only one oil hole leading from the main bearing journal to the rod bearing journal. Oil is supplied to the main bearing journals through oil galleries in the block. A cross-drilled crankshaft has two outlet holes for oil to reach the drilled passage that supplies oil to the rod journal.

spun bearing?

A stress of 40,000 psi (275,790 kPa) is considered maximum to avoid damaging bearing or housing. Bearing shells without enough crush may rotate with the shaft. The result is called a spun bearing

bore to size hone for clearance

Actual piston diameter: 4.028 in. Bore diameter: 4.028 in. Diameter after honing: 4.030 in. Amount removed by honing :0.002 in.

lubricating passages

After oil holes are drilled, the unneeded open ends may be capped by pipe plugs, steel balls, or cup-type soft plugs, often called oil gallery plugs. These end plugs in the oil passages can be a source of oil leakage in operating engines.

block detailing

All oil passages (galleries) should be cleaned by running a long bottle-type brush through all holes in the block. All tapped holes should be chamfered and cleaned with the correct size of thread chaser to remove any dirt and burrs.

Lubricating Passages

An engine block has many holes that carry lubricating oil to required locations. During manufacture, all oil holes, called the oil gallery, are drilled from outside the block.

Machining the Deck Surface of the Block

An engine should have the same combustion chamber size in each cylinder. Each piston must come up an equal distance from the block deck. The connecting rods are attached to the rod bearing journals of the crankshaft. Pistons are attached to the connecting rods. As the crankshaft rotates, the pistons come to the top of the stroke. When all parts are sized equally, all the pistons will come up to the same level. This can only happen if the block deck is parallel to the main bearing bores.

bearings fatigue

Bearings flex or bend slightly under changing loads, especially reciprocating engine bearings. Bearing metals tend to fatigue and break after being flexed or bent a number of times. Flexing starts fatigue and shows up as fine cracks in the bearing surface as the material is work hardened. These cracks gradually deepen to the bond between the bearing metal and backing metal. The cracks then cross over and intersect with each other.

Main bearing caps

Caps are not interchangeable or reversible because they are individually finished in place.

main bearing caps

Caps installed, main bearing bores and cam bearing bores are machined to the correct size and alignment.

cast crankshaft

Cast crankshafts are used in most production automotive engines. They may be cast in steel, nodular iron, or malleable iron. The major advantage of the casting process is that crankshaft material and machining costs are less than they are with forging. The crankshaft can be made close to the required shape and size, including all complicated counterweights. The only machining required on a carefully designed cast crankshaft is the grinding of bearing journal surfaces and the finishing of front and rear drive ends. Metal grain structure in the casting is uniform and random throughout; thus, the shaft is able to handle loads from all directions. Counterweights on cast crankshafts are slightly larger than counterweights on a forged crankshaft because the cast shaft metal is less dense and therefore somewhat lighter.

Main bearing Caps

Cast separately from the block. Machined and installed on the block for a final bore finishing operation.

counterweights

Crankshafts are balanced by counterweights, cast or forged as part of the crankshaft. A crankshaft that has counter-weights on both sides of the connecting rod journal is fully counterweighted. A fully counterweighted crankshaft is the smoothest and most durable design, but is also heaviest and most expensive. Most manufacturers do not use fully counterweighted crankshafts in an effort to lighten the rotating mass of the engine.

forged crankshaft

Crankshafts may be forged or cast. Forged crankshafts are stronger than the cast but are more expensive. Forged crankshafts have a wide separation line.Most high-performance forged crankshafts are made from SAE 4340 or a similar type of steel.Forging makes a very dense,tough crankshaft with the metal's grain structure running parallel to the principal direction of stress.

Sleeving the cylinder

Cylinder blocks with deep gouges can be salvaged by sleeving. The cylinder is bored to a dimension greatly oversize to almost match outside diameter of the cylinder sleeve. sleeve is pressed into cylinder.

Cooling passages

Cylinders are surrounded by cooling passages. These coolant passages around the cylinders are often called the cooling jacket.

cylinder boring

Cylinders wear in a taper, with most of the wear occurring at the top of the cylinder where the greatest amount of heat is created. The ridge is formed because this very top part of the cylinder is not worn by the rings. Cylinders should be measured across the engine (perpendicular to the crankshaft), where the greatest wear occurs.

engine bearings

Engine bearings are main supports for major moving parts of any engine. Engine bearings are important for the following reasons: The clearance between bearings and crankshaft is a major factor in maintaining proper oil pressure throughout the engine. Most engines are designed to provide maximum protection and lubrication to engine bearings above all else. Engine durability relies on bearing life. Bearing failure usually results in immediate engine failure. Engine bearings are designed to support the operating loads of the engine and, with the lubricant, provide minimum friction This must be achieved at all designed engine speeds. The bearings must be able to operate for long periods of time, when foreign particles are in the lubricant.

main bearing caps

Expansion force of combustion chamber gases will try to push the head off the top and the crank shaft off the bottom of the block,

the two ways engine manufactures balance an engine

Externally balanced Weight is added to the harmonic balancer (vibration damper) and flywheel or the flex plate. Internally balanced All rotating parts of the engine are individually balanced, including the harmonic balancer and flywheel (flex plate).

main bearing caps

Heavy-duty and high-performance engines use additional main bearing support bolts. A four-bolt, and even six-bolt, main cap can be of a cross-bolted design in a deep skirt block or of a parallel design in a shallow skirt block.

camshaft bearings continued

In many engines, each cam bearing is a different size—the largest is in the front and the smallest is in the rear. The cam bearing journal size must be checked and each bearing identified before assembly. The location of each new cam bearing can be marked on the outside of the bearing with a felt-tip marker to help avoid mixing up bearings. Marking in this way will not affect the bearing size or damage the bearing in any way. Cam bearings should be installed "dry" (not oiled) to prevent the cam bearing from moving (spinning) after installation. If the cam bearing were oiled, rotation of the camshaft could cause the cam bearing to rotate and block oil holes that lubricate the cam.

cooling passages

In most skirtless cylinder designs, the cooling passages extend nearly to the bottom of the cylinder. In extended skirt cylinder designs, the cooling passages are limited to the upper portion of the cylinder.

lifter bore bushings

Lifter bores in a block can be out-of-square with the camshaft, resulting in premature camshaft wear and variations in the valve timing from cylinder to cylinder. To correct for this variation, the lifter bores are bored and reamed oversize using a fixture fastened to the block deck to ensure proper alignment. Bronze lifter bushings are then installed and finish honed to achieve the correct lifter-to-bore clearance.

main bearing caps

Main bearing caps may have cast numbers indicating block position. If not, they should be marked.

Crankshaft parts

Main bearing journals Rod bearing journals Crankshaft throws Counterweights Keyways Oil passages

continued engine bearings

Most bearings are plain or sleeve bearing type. See Figure 29-56. Most bearing halves, or shells, do not have uniform thickness. Wall thickness of most is largest in the center, called the bearing crown. The bearing thickness then tapers to a thinner measurement at each parting line. See Figure 29-57.The tapered wall keeps bearing clearances close at the top and bottom of the bearing, which are the more loaded areas and allow more oil flow at the sides of the bearing. Both need a constant flow of lubricating oil. In automotive engines, the lubricating system supplies oil to each bearing continuously when the engine runs. Bearings and journals only wear when parts come in contact with each other or foreign particles are present.

if block is serviceable

Operation 1 Align boring or honing main bearing saddles and caps. Operation 2 Machining the block deck surface parallel to the crankshaft. Operation 3 Cylinder boring and honing.

Crankshaft Purpose and function

Power from expanding gases in the combustion chamber is delivered to the crankshaft through the piston, piston pin, and connecting rod The connecting rods and their bearings are attached to a bearing journal on the crank throw. The crank throw is offset from the crankshaft centerline. Force is applied to the crank throw after the crankshaft has moved past top center. This turning effort or torque rotates the crankshaft. The crankshaft rotates on the main bearings. These bearings are split in half so that they can be assembled around the crankshaft main bearing journals.

main bearing caps

Production engines usually use two bolts to hold the main bearing cap.

crank inspection

Shaft damage includes scored bearing journals, bends or warpage, and cracks. Damaged shafts must be reconditioned or replaced. The crankshaft is one of the most highly stressed engine parts. The stress on the crankshaft increases by four times every time the engine speed doubles. Any sign of a crack is cause to reject the crankshaft. Most cracks can be seen during a close visual inspection. Crankshafts should also be checked with Magnaflux, which will highlight tiny cracks that would lead to failure.

cooling passages

Some engines are built with Siamese cylinder bores where the cylinder walls are cast together without a water jacket (passage) between the cylinders.This design improves the strength and stability but can reduce the cooling around the cylinders.

Wet cylinder sleeves

Some engines have die-cast aluminum blocks with replaceable cast iron cylinder sleeves. The sleeves are sealed at the block deck and at their base. Coolant flows around the cylinder sleeve, so this type of sleeve is called a wet cylinder.

bearing embeddability

Some foreign particles get into the bearings, which must be capable of embedding them into the bearing surface so they do not score the shaft. To fully embed the particle, the bearing material gradually works across the particle, completely covering it. The property that allows it to do this is called embeddability.

what is a oil jet

Some turbocharged gasoline engines and many diesel engines have an oil jet which directs a shot of oil directly to the under side of the piston crown. The spray of oil not only lubricates, but helps reduce piston temperatures.

bearing comfortability

The ability of bearing materials to creep or flow slightly to match shaft variations is called conformability. The bearing conforms to the shaft during the engine break-in period. Automatic processing has achieved machining tolerances that keep the shaft very close to the designed size.

bearing spread and crush

The bearing shell has a slightly larger arc than does the bearing housing. This difference is called bearing spread and it makes the shell 0.005 to 0.020 inch (0.125 to 0.500 millimeter) wider than the housing bore. Spread holds the bearing shell in the housing while the engine is being assembled. When the bearing cap is tightened, the ends of the two bearing shells touch and are forced together. This force is called bearing crush. Crush holds the bearing in place and keeps the bearing from turning when the engine runs. Crush must exert a force of at least 12,000 psi (82,740 kPa) at 250°F (121°C) to hold the bearing securely in place.

bearing clearances

The bearing-to-journal clearance may be from 0.0005 to 0.0025 inch (0.025 to 0.060 mm), depending on the engine. Doubling the journal clearance will allow more than four times as much oil to flow from the edges of the bearing The oil clearance must be large enough to allow an oil film to build up, but small enough to prevent excess oil leakage, which would cause loss of oil pressure. A large amount of oil leakage at one of the bearings would starve other bearings farther along in the oil system. This would result in the failure of the oil-starved bearings

camshaft bearings

The camshaft in pushrod engines rotates in sleeve bearings that are pressed into bearing bores within the engine block. Overhead camshaft bearings may be sleeve-type bushings called full round bearings or split-type (half-shell) bearings. In pushrod engines, the cam bearings are installed in the block.

Crankshaft thrust loads

The crankshaft also has to be able to absorb thrust loads from the clutch on a manual transmission vehicle or the torque converter on a vehicle equipped with an automatic transmission. Thrust loads are forces that push and pull the crankshaft forward and rearward in the engine block. A thrust bearing supports these loads and maintains the front-to-rear position of the crankshaft in the block. See Figure 29-35.The thrust surface is usually located at the middle on one of the end main bearings. On most engines, the bearing insert for the main bearing is equipped with thrust bearing flanges that ride against the thrust surface.

crank oiling holes

The crankshaft is drilled, as shown in Figure 29-47, to allow oil from the main bearing oil groove to be directed to the connecting rod bearings. The oil on the bearings forms a hydrodynamic oil film to support bearing loads. Some oil may be sprayed out through a spit or bleed hole in the connecting rod. The rest leaks from the edges of the bearing. It is thrown from the bearing against the inside surfaces of the engine. Some oil thrown from the crankshaft bearings will land on the camshaft to lubricate the lobes. A part splashes on the cylinder wall to lubricate the piston and rings. Stress tends to concentrate at oil holes drilled through the journals. These holes are usually located where loads and stresses are the lowest. The edges of oil holes are carefully chamfered to relieve as much stress concentration as possible.

main bearing journals

The crankshaft rotates in the cylinder block on main bearings, which support the crankshaft and allow it to rotate easily without excessive wear. number of cylinders usually determines number of main bearing journals.

Block Deck

The cylinder head is fastened to the block deck. The deck has a smooth surface to seal against the head gasket. Bolt holes are positioned around the cylinders to form an even holding pattern. Four, five, or six head bolts are used around each cylinder in automobile engines. These bolt holes go into reinforced areas within the block that carry the combustion pressure load to the main bearing bulk-heads. Additional holes in the block are used to transfer coolant and oil.

Engine Block service

The engine block is the foundation of the engine. All parts of the block must be of the correct size and they must be aligned .The parts must also have the proper finishes if the engine is to function dependably for a normal service life. Blueprinting is the reconditioning of all the critical surfaces and dimensions so that the block is actually like new. After a thorough cleaning, the block should be inspected for cracks or other flaws before machine work begins.

main bearing caps

The engine is held together with the head bolts and main bearing cap bolts screwed into bolt bosses and ribs in the block.

Main bearing caps

The extra bolts on the main bearing cap help to support the crankshaft during high combustion pressures and mechanical loads, especially during high-engine speed operation.

main bearing bores

The main bearing bores of a warped block usually bend into a bowed shape. The greatest distortion is in the center bores. The main bearing bores gradually bow from the cylinder head and elongate vertically. This means that the bearing bore becomes smaller at the center line as the block distorts, pinching the bore inward at the sides.

Main Bearing Housing Bore Alignment

The main bearing journals of a straight crankshaft are in alignment. If the main bearing housing bores in the block are not in alignment, the crankshaft will bend as it rotates, leading to premature bearing failure and possibly a broken crankshaft.

plateau honing

The process of using both coarse and fine stones is called

block manufacturing

The trend is to make blocks with larger cores, using fewer individual pieces. Oil-sand cores are forms that shape internal openings and passages in block. Before casting, the cores are supported within a core box. The core box also has a liner to shape the outside of the block. Special alloy cast iron is poured into the box. It flows between the cores and the core box liner. As the iron cools, the core breaks up. When the iron has hardened, it is removed from the core box, and the pieces of sand core are removed through the openings in the block by vigorously shaking the casting. These openings in the block are plugged with core plugs. One way to keep weight as low as possible is to make the block with minimum wall thickness. Cast iron used with thin-wall casting techniques has higher nickel content and is harder than cast iron previously used. Engine designers have used foundry techniques to make engines lightweight by making the cast-iron block walls and bulkheads only as heavy as necessary to support their required loads.

bearing material

Three materials are used for automobile engine bearings: Babbitt, copper-lead alloy, and aluminum. A layer of the bearing materials 0.010 to 0.020 inch (0.25 to 0.50 mm) thick is applied over a low-carbon steel backing. An engine bearing is called a bearing shell, which is a steel backing with a surface coating of bearing material. The steel provides support needed for the shaft load. The bearing material meets the rest of the bearing operating requirements.

what is an offset crankshaft

To reduce side loads, some vehicle manufacturers offset the crankshaft from center. For example, if an engine rotates clockwise as viewed from the front, the crankshaft may be offset to the left to reduce the angle of the connecting rod during the power stroke. The offset usually varies from 1/16 inch to 1/2 inch, depending on make and model. Most gasoline engines used in hybrid gasoline/electric vehicles use an offset crankshaft.

torque plates

Torque plates are thick metal plates that are bolted to the cylinder block to duplicate the forces on the block that occur when the cylinder head is installed. Though not all shops use torque plates during boring their use during the final dimensional honing operation is very beneficial.

Aluminum block

Used for some cylinder blocks; nonmagnetic and lightweight .Cast-aluminum blocks may have steel cylinder liners. The cast-iron cylinder sleeves are either cast into the aluminum block during manufacturing or pressed into the aluminum block.

determining the condition of the main bearing bores diameter

Using a telescoping gauge, measure each bore in at least two directions. Check the service information for the specified main bearing bore diameter. The bearing bore should not vary by more than one-half of a thousandth of an inch or 0.0005 inch (0.0127 mm).

Lubricating passages

When a curved passage is needed, intersecting drilled holes are used. In some engines, plugs are placed in the oil holes to direct oil to another point before it comes back to the original hole, on the opposite side of the plug.

rod bearing journals

also called crankpins, are offset from centerline of crank

aluminum block main bearing caps

are made of cast iron to provide the required stregth

Cylinder honing

breaking hard surface glaze on the cylinder wall with a hone before installing new piston rings. The cylinder wall should be honed when the wall is wavy or scuffed.

how to calculate compression ratio

cyl vol + vol at TDC/volume at TDC

The Monoblock

design means that the cylinder, water jacket, main bearing supports (saddles), and oil passages are all cast as one structure for strength and quietness.

determining the condition of the main bearing bores

first step is to determine if the bore alignment in the block is straight. These bores are called the saddles. A precision ground straightedge and a feeler gauge are used to determine the amount of warpage. Variation along the entire length of the block should not exceed 0.0015 inch (0.038 mm). If the block saddles exceed one-and-a-half thousandth of an inch distortion, then align honing is required to restore the block.

surface finishing

grit size and pressure affects the finish. lighter pressure smoother finish. Chrome—#180 grit (25 to 35 micro inches) Cast iron—#200 grit (20 to 30 micro inches) Moly—#220 grit (18 to 25 micro inches)

other aluminum block design

has the block die cast from silicon aluminum alloy with no cylinder liners. Pistons with zinc-copper-hard iron coatings are used in these aluminum bores (some Porsche engines).

cross hatch

he hone is stroked up and down in the cylinder as it rotates. This produces a crosshatch finish on the cylinder wall. The angle of the crosshatch should be between 20 and 60 degrees. Higher angles are produced when the hone is stroked more rapidly in the cylinder.

what is a piston

is what transfers the combustion energy to the crank via connecting rod to produce motion

what is a connecting rod

its what connects the piston to the crankpin/connecting rod journal

piston design

low cost low performance have flat head pistons. higher power engine's may have raised domes or pop-ups on the piston head this helps increase compression ratio. other engines may use and depression or a dish varying depths provide different compression ratios. direct injection engines have special pistons

how to find ring gap

multiply bore size by 0.004

crank ring lan can cause

oil consumption, blow by, sometimes misfire at certain rpm

deglazing hone

removes the hard surface glaze remaining in the cylinder. It is a flexible hone that follows the shape of the cylinder wall, even when the wall is wavy. not used to straighten cylinder

long block

short block plus heads not given it comes with a cam

Dry cylinder sleeves

sleeves are not in contact with the coolant passages

Engine Blocks

supporting structure for entire engine. made from gray cast iron or from cast or die-cast aluminum alloy. The gray color is result of the 3% carbon in the form of graphite in the cast iron. The carbon in iron allows for easy machining, often without coolant. The graphite in iron also has lubricating properties. Newer blocks use thinner walls to reduce weight.

piston when cold

the piston diameter is actual slightly miss shaped so when heated it expands close to a perfect circle this is more for oem to meet emission's not so much aftermarket

what are spark plugs

they are what ignite your gas

what is a piston ring

they are what seal space between piston and cylinder wall keeping pressure. to compression rings and one oil ring made up to three parts

determining engine displacement

to calculate engine displacement in cubic inches you will need to know; cylinder bore diameter, and stroke length. bore diameter squared*stroke*0.7854(pie/4)*# of cylinders=displacement. EX: 4 squared*3*0.7854*6=226cu.in

block cleaning and prep for assembly

use a sandpaper cone to chamfer the top edge of the cylinder. Cleaning the honed cylinder wall is an important part of the process. If any grit remains on the cylinder wall, it will rapidly wear the piston rings, and cause premature failure of the reconditioning job. The best way to clean honed cylinders is to scrub the cylinder wall with a brush using a mixture of soap or detergent and water. The block is scrubbed until it is absolutely clean

Sizing hone

used to straighten the cylinder and to provide a suitable surface for the piston rings.The cylinders must be honed a minimum of 0.002 inch (0.050 mm)

what is a piston pin

what attaches connecting rod to piston

short block

whole bottom end, engine block plus rotating assembly