A Project Report

on

(Prevention of Scoring on Bearing Shell)

(Quality Assurance)

submitted in fulfillment of the requirements of the degree of

BACHELOR OF TECHNOLOGY

Supervised By:

Mr. Rakesh KumarSubmitted By:

Suraj Kumar GuptaB.Tech (ME)

8th semester

DEPARTMENT OF MECHANICAL ENGINEERING

JAGANNATH UNIVERSITY, CHAKSU

JAIPUR (RAJ.) INDIA

Mar-2014

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CERTIFICATE

This is to certify that the Project entitled “Prevention of scoring in bearing shell

undergoing in Tata Motors, Jamshedpur” being submitted by Suraj Kumar Gupta in

fulfillment for the award of Degree of Bachelor of Technology 8th Sem in Mech Engineering

Jagannath University, Jaipur, under my supervision and guidance, is hereby approved for submission.

Date: 21/03/2014

Mr. Rakesh Kumar

Place: Jagannath university

Department of Mechanical Engineering

Jagannath University, Chaksu

Jaipur (Raj.)

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ACKNOWLEDGEMENT

The work on this project started from month of Jan 2014.Since then, a large number of

operators of engine factory have made valuable suggestions and ideas which I have incorporated

in this work. It is not possible for me to acknowledge all of them individually. I take this

opportunity to express my gratitude to them. However, I am specially thanked to Mr. Ohm

Prakash (Manager, crankshaft line Tata Motors Jamshedpur) for helping me in this project

building.

I am indebted towards Mr. Rishikesh Dabhade (Sr. Manager, crankshaft line Tata

Motors, Jamshedpur) who helped me to make this project more successful. He always guided me

during the course of this project and gave me valuable advice and were good enough to find time

for fruitful discussion.

Suraj Kumar Gupta

(B.Tech. 8th Sem)

Department of Mechanical Engineering

Jagannath University, Chaksu

Jaipur (Raj.)

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TABLE OF CONTENTS Page No

i. Introduction to Tata Motors 5ii. Tata Motors, Jamshedpur Plant 6

iii. Project Description 9iv. Basic of Bearing 10v. What is BI? 12

vi. Month wise bearing inspection 13vii. Types of Scoring 14

viii. MB wise scoring 16ix. Bearing inspection in Feb’14 17x. Possible causes of bearing scoring 19

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Introduction to Tata Motors

Tata Motors Limited (formerly TELCO, short for Tata Engineering and Locomotive Company) is an Indian multinational automotive manufacturing company headquartered in Mumbai, Maharashtra, India and a subsidiary of the Tata Group. Its products include passenger cars, trucks, vans, coaches, buses, construction equipment and military vehicles. It is the world's seventeenth-largest motor vehicle manufacturing company, fourth-largest truck manufacturer and second-largest bus manufacturer by volume.

Tata Motors has auto manufacturing and assembly plants in Jamshedpur, Pantnagar, Lucknow, Sanand, Dharwad and Pune in India, as well as in Argentina, South Africa, Thailand and the United Kingdom. It has research and development centres in Pune, Jamshedpur, Lucknow and Dharwad, India, and in South Korea, Spain, and the United Kingdom. Tata Motors' principal subsidiaries include the British premium car maker Jaguar Land Rover (the maker of Jaguar, Land Rover and Range Rover cars) and the South Korean commercial vehicle manufactuer Tata Daewoo. Tata Motors has a bus manufacturing joint venture with Marcopolo S.A. (Tata Marcopolo), a construction equipment manufacturing joint venture with Hitachi (Tata Hitachi Construction Machinery) and a joint venture with Fiat which manufactures automotive components and Fiat and Tata branded vehicles.

Founded in 1945 as a manufacturer of locomotives, the company manufactured its first commercial vehicle in 1954 in a collaboration with Daimler-Benz AG, which ended in 1969. Tata Motors entered the passenger vehicle market in 1991 with the launch of the Tata Sierra, becoming the first Indian manufacturer to achieve the capability of developing a competitive indigenous automobile.[6] In 1998 Tata launched the first fully indigenous Indian passenger car, the Indica, and in 2008 launched the Tata Nano, the world's cheapest car. Tata Motors acquired the South Korean truck manufacturer Daewoo Commercial Vehicles Company in 2004 and purchased Jaguar Land Rover from Ford in 2008.

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Tata Motors, Jamshedpur Plant

The Jamshedpur facility, Tata Motors' first, was established in 1945 to manufacture steam locomotives. It led the company's foray into commercial vehicles in 1954. It has been modernized through the decades, with a particularly intense scale in the last 10 years and has led the company's evolution into a manufacturer of global repute.

This world-class facility is equipped with:

State-of-the-art equipment and assembly lines to produce a truck every 5 minutes

Over 200 models, ranging from multi-axle trucks, tractor-trailers, tippers, mixers and special application vehicles, catering to civilian and defence requirements

3D visualisation of new models

Engine assembly shop, capable of supplying upto 200 engines per day

Modern testing facilities

The plant manufactures Tata Motors' entire range of medium and heavy commercial vehicles, including the Tata Prima, both for civilian and defence applications - over 200 truck variants, ranging from multi-axle trucks, tractor-trailers, tippers, mixers and special application vehicles. Besides India, these vehicles are sold in South Africa, Russia, Myanmar, the SAARC region and the Middle East. On February 19, 2013, Jamshedpur Plant rolled out its two millionth truck.

The plant houses a world class Engineering & Research Centre. The centre is responsible for the conceptualisation and integration of Tata Motors' current and future truck range. The centre undertakes complex digital design through 3D visualization of new truck models, including that of its features and electrical systems. It also houses a comprehensive facility for benchmarking, prototype planning, vehicle assembly, chassis fabrication and a customisation unit. The testing unit also includes engine performance testing, indoor and outdoor vehicle testing, NVH (Noise, Vibration, Harshness) testing, durability testing and other performance related developments.

The state-of-the-art Engine Factory manufactures the Tata 697/497 naturally aspirated and turbo charged engines, with a capacity of supplying upto 200 engines per day.

The Vehicle Factory's main assembly line rolls out one truck every 5 minutes. Two other lines are dedicated to the Prima range, Multi-axle, special purpose vehicles and for meeting the requirements of the defence sector.

The chassis frames are supplied by the Frame Factory, which is equipped with a 5000 Ton Siempelkamp press to manufacture frames upto 6.2 metre wheel base.

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The fully equipped Foundry supplies high-grade SG Iron Castings and is rated as one of the highly automated foundries in the world. It manufactures all critical automobile castings, viz. Cylinder Block, Cylinder Head etc. Its sophisticated Kunkel Wagner High Pressure Moulding line has a rated production capacity of 90 moulds/ hour. The melting shop has Medium Frequency Induction Furnaces for melting and Channel Furnaces for holding while the pouring is done by a Channel Press Pour coupled with a Steam Inoculation Dispenser. The core shop has a state-of-the-art Cold Box Machine, making four cores per minute. It has elaborate sand and metallurgical laboratories. In 1993, the Foundry was ISO 9002 certified by the Bureau Veritas Quality International, followed by QS 9000 and  TS: 16949.

The Cab & Cowl Factory is equipped with an automated Centralized Paint Shop with a provision for metallic painting and Centralized Trim Lines, which help improve logistics flow.

The facility also houses a Shower testing facility in vehicle dispatch area, an NABL-accredited Metrology lab, a Clean room for CRDI engines to ensure a dust-free environment for fitment of critical parts and a world-class Technical Training Centre and Driver Training centre. The Plant incorporates a flexible approach to manufacturing, such that it is ready to respond rapidly to changing customer needs.

TML Drivelines Limited was established on March 13, 2000 as a subsidiary of Tata Motors by taking over operations of Tata Motors' erstwhile Axle and Gearbox Divisions. It is currently the market leader in medium and heavy commercial vehicles axles in India with an installed capacity of over two lakh axles per annum. The Company's product range includes Front Steer axles - both live and normal, Rear Drive axles and dummy/ trailer axles. It is the leading supplier of M&HCV axles to the Jamshedpur and Lucknow plants of Tata Motors.

It has state-of-the-art manufacturing facilities for making all major axle components such as Front Axle Beam, Stub Axles, Front & Rear Wheel Hubs, Differential, Axle Gears (Crown Wheel, Pinion, Bevel Gear & Shaft Gear), Banjo Axle Beam, Swivel Heads, Constant Velocity Shafts etc. The Quality System of TML Drivelines Limited is certified under ISO/ TS-16949. On the environmental and safety front, it received OHSAAS-18001 in 1999 and ISO 14001 certification in 2004.

TML Drivelines Limited has proven skills in manufacturing axles from component level to assembly & testing. As one of the most modern forging set-ups in the country, the Forge is equipped with the 40,000 mkg Beche Hammer and state-of-the-art presses from Kurimoto of Japan. It produces critical forgings like crankshafts, front axle beams and rear axle shafts. The Forge has been certified as ISO 9002 and QS 9000 by the BVQI.

While making technological, product and service advancements, Jamshedpur Plant has been deeply committed to the communities among which it operates. Working closely with various NGOs, it has pioneered initiatives in Health, Education, Livelihood and Environment. These initiatives have resulted in significant progress in community and social forestry, sustainable

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development of wastelands, road construction, rural health and education, development of rural industries, water supply and family planning. A signatory to the UN Global Pact, it also takes various initiatives in human rights protection, labour standards, environmental issues, modern effluent treatment facilities, sanitation drives, soil and water conservation programmes, tree plantation drives etc.

Engine Factory has following shops:-

Machining shops

1. Cylinder block line

2. Crank shaft line

3. Cam shaft line

4. Cylinder head line

Assembly line

Testing and Dispatching

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PROJECT DESCRIPTION:

In the last month January 2014, during Bearing Inspection it has been found that bearing shells of many engines got scored. Total numbers of engines (having scored bearing shells) were 23 in January, while in previous year, each month had maximum 4 Nos. engines having scored bearing shells. Scoring in bearing shells of MBs & CPS found and in some engines also on journals of

MBs & CPs, due to which many engines were brought for BI (Bearing Inspection). This project

is undertaken to determine and eliminate the causes of bearing shells scoring and reduce the

chances of bearing failure. If bearing shells did not get scored then at least every engines which are brought for BI had circumferential lines on inner surface of bearing shells and/or on journal. Tata Motors produces the product based on WCQ (World Class Quality), so scoring on bearing shells is major problem to achieve world class quality. To eliminate or minimize this problem ( in other words to achieve WCQ) we have to work on six sigma project.

Six Sigma seeks to improve the quality of process outputs by identifying and removing the causes of defects (errors) and minimizing variability in manufacturing and business processes.

A six sigma process is one in which 99.99966% of the products manufactured are statistically expected to be free of defects (3.4 defective parts/million).

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Basic of Bearing

No engine can run without bearings. Bearings are used in engines to support and protect rotating parts and allow them to turn freely. The connecting rod must be able to spin freely on the crankshaft. The crankshaft must be able to spin freely in the engine block.

Connecting rod bearings and the crankshaft main bearings are called split-sleeve types, which means they are in two halves, called inserts, slippers or shells.

These precision-inserts have a steel back with a very thin layer of bearing material bonded to it. The bearing material is an alloy that can include metals such as tin, lead, aluminium and copper.

Bearings designed for light duty may be made of white metal. It’s an alloy of tin and lead, with small amounts of copper and antimony.

Alloys of tin and aluminium improve the load-carrying capacity for intermediate applications.

Copper-lead alloys give even more improvements. They’re used in applications such as diesel engines, and high-performance vehicles.

Bearings need a difficult mix of properties. They must be hard enough to resist wear, but soft enough not to damage the shaft.

The soft bearing surface also allows any hard abrasive particles to become embedded in the surface. They can become so deeply embedded, they are prevented from touching the rotating shaft by the film of oil.

It is the mix of metals, tin, lead, copper and others, into an alloy that makes this combination of hardness and softness.

In a main bearing, the upper half of the bearing fits into a machined section of a crankcase web. The lower half is carried in the bearing cap which bolts onto the crankcase web.

In a connecting rod bearing, its upper half is carried in the big end of the connecting rod. The lower half is in the connecting rod cap.

One main bearing has thrust faces which accept the end movement of the crankshaft. These can be in the form of flanges that are part of the beanng. Alternatively, a separate thrust washer can be fitted into a machined recess in each side of the bearing cap. Sometimes a mating recess for each side is machined into the cylinder block and mating halves fitted to both.

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Under normal running conditions, spinning shafts ride on a microscopic wedge of oil.

Oil flows through a long gallery in the cylinder block. Each main bearing has its own oil supply passageway from this gallery. Passageways drilled in the crankshaft carry oil from the main bearing journals to rod journals.

Oil flow maintains the oil wedge between the shaft and bearing, and carries away particles that could cause wear.

Engine manufacturers specify the clearance required between the bearing material and the crankshaft. This clearance gives the best combination of oil pressure and flow.

As clearance increases with wear, oil flow increases, causing oil pressure to drop. Then the shaft may rub against the bearing surface and wear even faster.

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What is Bearing Inspection ( BI ) ?

Bearing Inspection is an important activity after engine testing. Every 50 th engine after testing is brought in rectification area for BI where all the MBs caps & con rod caps are untorqued and then remove them from engines.

After that, all MBs & CPs and their caps including their bearing shells are checked and verified with QA Inspector for dent mark or any type of damage/scratch mark on the bearing shells.

Since BI found NOK in many engines so every 25 th engine after testing is going to collect for BI.

BEARING INSPECTION OPERATION SEQUENCE

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MONTHWISE BEARING INSPECTION DETAILS

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Types of scoring

• Deep dent mark

Light dent mark

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• Scratch

Circumferential scoring

• Deep & Light lines

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MB wise scoring (Oct’13 to Jan ‘14)

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MB18%

MB215%

MB314%

MB412%

MB517%

MB614%

MB720%

BEARING INSPECTION IN FEB’14

ENGINE NO.

CRANK SHAFT NO.

MB1 MB2 MB3 MB4 MB5 MB6 MB7

BVY1575 BFc14A0398 LS DS

BVY1600 BFc14A0488

BVY1625 T14A0564 LS

BVY1650 BFc14A0486

BVY1675 T14A0528

BVY1700 T14A0604 DS

BVY1725 BFc140424 LS

BVY1745 BFc14A0695 LS

BVY1775 T14A0567 L

BVY1800 T14A0248 L L CS

BVY1825 BFc14A0543 L L

BVY1850 BFc14A0550 LS

BVY1815 T14A0554 L L L L L L

BVY1897 T14A0208 LS

BVY1818 T14A0366

BVY2350 T14B0276 LS

BVY2400 T14B0156

BVY2450 BFc14A0697 L L

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BVY2700 BFc14B0052

BVY2750 BFc14B0196

LS : Light Scored

DS : Deep Scored

CS : Circumferential scored

L : Lines

Possible causes of bearing scoring

Dirt

Chips

Insufficient oil supply

Overheating

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Improper machining of engine components

Misalignment of engine components

Assembly errors

Bearing clearances

CAUSES OF ENGINE BEARING SCORING

Dirt& Chips: Dirt contamination often causes premature bearing failure. When dirt or other abrasives find their way between the crankshaft journal and bearing, it can become embedded in the soft bearing material. The softer the bearing material, the greater the embedability, which may or may not be a good thing depending on the size of the abrasive particles and the thickness of the bearing material.

If a particle is small and becomes deeply embedded in a relatively soft bearing material, it may cause no damage to the crankshaft journal. But if it displaces bearing material around itself or protrudes above the bearing surface, it can score the crankshaft.

Overheating: Heat is another factor that accelerates bearing wear and may lead to failure if the bearings get hot enough. Bearings are primarily cooled by oil flow between the bearing and journal. Anything that disrupts or reduces the flow of oil not only raises bearing temperatures but also increases the risk of scoring or wiping the bearing. Conditions that can reduce oil flow and cause the bearings to run hot include a worn oil pump, restricted oil pickup screen, internal oil leaks, a low oil level in the crankcase, aerated oil (oil level too high), fuel diluted oil from excessive blowby or coolant contaminated oil from internal coolant leaks.

Temperatures in excess of 620 degrees can melt away the lead in copper/lead bearings and those with babbitt overlays. Because copper does not melt until 1,980 degrees, burned copper/lead bearings will typically have a copper appearance instead of the normal dull gray appearance.

Misalignment is another condition that can accelerate bearing wear. If the center main bearings are worn more than the ones towards either end of the crankshaft, the crankshaft may be bent or the main bores may be out of alignment.

The straightness of the crankshaft can be checked by placing the crank on V-blocks, positioning a

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dial indicator on the center journal and watching the indicator as the crank is turned one complete revolution. If runout exceeds limits (the greater the shaft diameter, the greater the maximum amount of allowable runout), the crank must be straightened or replaced.

Main bore alignment can be checked by inserting a bar about .001 in. smaller in diameter than the main bores through the block with the main caps installed and torqued. If the bar does not turn easily, the block needs to be align bored. Alignment can also be checked with a straight edge and feeler gauge. A deviation of more than .0015 in. in any bore calls for align boring. Line boring must also be done if a main cap is replaced.

The concentricity of the main bores is also important, and should be within .0015 in. If not, reboring will be necessary to install bearings with oversized outside diameters.

Connecting rods with elongated big end bores can cause similar problems. If the rod bearings show a diagonal or uneven wear pattern, it usually means the rod is twisted. Rods with elongated crank journal bores or twist must be reconditioned or replaced. On some newer engines such as Ford's 4.6L V8 with powder metal rods and "cracked" caps, rods with elongated bores cannot be reconditioned by grinding the caps because the caps do not have a machined mating surface. So the big end bores must be cut to accept bearings with oversized outside diameters if the bores are stretched or out-of-round.

Uneven bearing wear due to misalignment can also result if the crankshaft journals are not true. To check the roundness of the crank journals, measure each journal's diameter at either bottom or top dead center and again at 90 degrees either way. Rod journals typically experience the most wear at top dead center. Comparing diameters at the two different positions should reveal any out-of-roundness if it exists. Though the traditional rule of thumb says up to .001 in. of journal variation is acceptable, many engines cannot tolerate more than .0002 to .0005 in. of out-of-roundness.

To check for taper wear on the journals (one end worn more than the other), barrel wear (ends worn more than the center) or hourglass wear (center worn more than the middle), measure the journal diameter at the center and both ends. Again, the generally accepted limit for taper wear has usually been up to .001 in., but nowadays it ranges from .0003 to .0005 in. for journals two inches or larger in diameter.

The journal diameter itself should be within .001 in. of its original dimensions, or within .001 in. of standard regrind dimensions for proper oil clearances with a replacement bearing. If a journal has been previously reground, there is usually a machinists mark stamped by the journal. A 10, 20 or 30 would indicate the crank has already been ground to undersize, and that further regrinding may be out of the question depending on how badly the crank is worn.

CRANKSHAFT REFINISHING

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Any crankshaft that does not meet all of the above criteria or has grooves, scratches, pitting or galling on the surface must be ground undersize to restore the journals. The journals should also be polished to provide a smooth surface (10 microinches or less is recommended), and the oil holes chamfered to promote good oil flow to the bearings.

Ron Thompson, a bearing engineer at Federal-Mogul says improper crankshaft finish can be especially hard on bearings. If using traditional polishing equipment, he recommends a two-step polishing procedure to achieve an optimum finish. First, the journals should be polished in the "unfavorable" direction (opposite the direction of rotation) with #280 grit, then finished in the "favorable" direction (same direction as rotation) with #320 grit.

Steve Williams of K-Line Industries, Holland, MI says the type of polishing procedure will vary depending on the type of metal in the crankshaft and how it is ground. "With our equipment, we do not recommend an unfavorable/favorable polish. We recommend favorable only. A 30 second polish using our 15 micron tape will produce journal finishes in the 3 to 6 microinch range."

ENGINE BEARING MISASSEMBLY

Misassembly can be another cause of premature bearing failure. Common mistakes include installing the wrong sized bearings (using standard size bearings on an undersize crank or vice versa), installing the wrong half of a split bearing as an upper (which blocks the oil supply hole and starves the bearing for oil), getting too much or not enough crush because main and/or rod caps are too tight or loose, forgetting to tighten a main cap or rod bolt to specs, failing to clean parts thoroughly and getting dirt behind the bearing shell when the bearing is installed.

Corrosion can also play a role in bearing failure. Corrosion results when acids accumulate in the crankcase and attack the bearings causing pitting in the bearing surface. This is more of a problem with heavy-duty diesel engines that use high sulfur fuel rather than gasoline engines, but it can also happen in gasoline engines if the oil is not changed often enough and acids are allowed to accumulate in the crankcase. Other factors that can contribute to acid buildup include a restricted or plugged PCV system, engine operation during extremely cold or hot weather, excessive crankcase blowby (worn rings or cylinders) or using poor quality oil or fuel.

Babbitt and lead are more vulnerable than aluminum to this type of corrosion, so for engine applications where corrosion is a concern aluminum bearings may offer better corrosion resistance.

ENGINE BEARING CLEARANCES

Proper clearances are another factor that are extremely important bearing longevity and oil pressure. Crankshaft bearings generally need at least a .0001 inch thick oil film between themselves and their journals to prevent metal-to-metal contact. This requires assembly clearances that are loose enough so oil can flow into the gap between the bearing and journal to

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form an oil wedge that can support the crankshaft. The clearance must also be sufficient to allow enough oil flow to cool the bearings. But the clearance must not be too great otherwise the oil will escape before it can form a supporting wedge.

Excessive bearing clearances (more than about .001 inch per inch of diameter of the crankshaft journal) can allow a drop in oil pressure that can adversely effect lubrication elsewhere in the engine such as the camshaft and upper valvetrain. Excessive clearances also increase engine noise and pounding, which over time can lead to bearing fatigue and failure. Fatigued bearings will typically be full of microscopic cracks and have flaking material on the surface.

The amount of clearance between the bearings and crank journals will obviously vary depending on the application and the preferences of the engine rebuilder. You may want closer tolerances to maximize oil pressure if you plan to use a lower viscosity motor oil such as 5W-20, or you may want to run a heavier racing oil such as 20W-50, in which case you will need looser bearing clearances. Thinner oils reduce friction and improve fuel economy but also require closer bearing clearances to maintain good oil pressure.

One large production engine rebuilder says they try to build all their passenger car and light truck engines with about .001 to .002 inch clearance in the main and rod bearings. This compares to as much as .004 inch of clearance that may have been present in the OEM engine. But on some engines, such as the General Motors 173, more than .0015 inch of clearance can result in noise problems.

ENGINE BEARING ECCENTRICITY

Most crankshaft bearings are designed with a certain amount of "eccentricity" so oil can more easily form a wedge to support the crankshaft. The shell is typically about 0.00013 to 0.0005 inches thicker at the crown than the parting line. This allows the oil to get under the crank as the crank starts to turn, lifting it off the bearing so it can glide on a film of oil.

Increasing the amount of eccentricity can increase oil flow for greater bearing cooling and longevity, which is why many racing bearings have extra eccentricity. But at low rpm, too much eccentricity may cause a slight drop in oil pressure. Since many production engine rebuilders test newly assembled engines on a simulator or dyno, bearings with a high amount of eccentricity may give the false impression that something is amiss because the oil pressure readings may be lower than "normal."

ENGINE BEARING MATERIALS

At the original equipment level, the use of aluminum main and rod bearings is growing for a variety of reasons. One is that aluminum bearings are less expensive to manufacturer than bimetal or trimetal copper/lead bearings. Switching to aluminum also gets rid of lead, which is an

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environmental concern for manufacturers. But there are many other reasons, too.

"Overplated bearings tend to trap and hold dirt that can score the crankshaft.

"Although most rebuilders still prefer copper/lead because it is a more forgiving material, others prefer to use the same bearing material as the original bearings.

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References

www.tatamotors.com

www.wikipedia.org

www.google.com

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