chap29 pps Automotive technology at University of Cambridge

start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 29, the reader should be able to: • • • • Prepare for Engine Repair (A1) ASE certification test content area “C” (Engine Block Diagnosis and Repair) Describe the types of engine blocks and how they are manufactured List the machining operations required on most engine blocks List the steps necessary to prepare an engine block for assembly Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 29, the reader should be able to: • • • Describe the purpose and function of a crankshaft Explain how crankshafts are machined and polished Discuss engine bearing construction and installation procedures Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: aluminum • amplitude babbitt • ball-type deglazing hone • bank • bearing crown • bearing shell • bedplate • block deck • bores case hardening • compacted graphite iron (CGI) • conformability • cooling jacket • copper–lead alloy • core plugs • corrosion resistance • counterweights • crankshaft centerline • crosshatch finish • crush decking the block • deglazing hone • dry cylinder sleeve elastomer • electroplating • embedability Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: fatigue life • flying web • freeze plugs • frequency • frost plugs • full round bearings • fully counterweighted grit size • half-shell bearings • hub • inertia ring left-hand dipstick • monoblock • nitriding oil gallery • oil gallery plugs • overlay • plain bearing • plateau hone • precision insert-type bearing shells rebore • resonate Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: saddles • score resistance • Siamese cylinder bores • sizing hone • sleeve bearing • sleeving • splay angle • split-type bearings • spread • spun bearing tuftriding • wet cylinder sleeve • work hardened Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 ENGINE BLOCKS The engine block, which is the supporting structure for the entire  engine, is made from gray cast iron or from cast or die­cast  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.  All other engine parts are mounted on or in the block. This large  casting supports the crankshaft and camshaft and holds all the  parts in alignment. 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 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Large­diameter holes in the block casting form the cylinders to  guide the pistons. The cylinder holes are called bores because they  are made by a machining process called boring Combustion pressure loads are  carried from head to the crank­ shaft bearings through the block  structure Figure 29–1 The cylinder block usually extends from the oil pan ralls at the bottom to the deck surface at the top The block has webs, walls, and  drilled passages to contain coolant  and lubricating oil and keep them  separate.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Mounting pads or lugs on the block transfer the engine torque  reaction to the vehicle frame through attached engine mounts A large mounting surface at the rear of the engine block is used  for fastening a bell housing or transmission. The cylinder head(s)  attaches to the block The attaching joints are sealed so that they do not leak. Gaskets  are used in the joints to take up differences that are created by  machining irregularities and that result from different pressures  and temperatures Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Block Manufacturing  Cast­iron cylinder block casting tech­ nology continues to be improved. The trend is to make blocks with  larger cores, using fewer individual pieces Oil­sand 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.  10 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 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.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 12 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 29–71 The tang and slot help index the bearing in the bore A lip or tang locates the bearing shell in the housing The design also includes bearing spread and crush Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Figure 29–72 Bearing spread and crush 12 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 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 Figure 29–73 Bearings are thinner at the parting line faces to provide crush relief Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Figure 29–74 Spun bearing The lower cap bearing has rotated under the upper rod bearing 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 CAUTION: Some bearings may have oil holes in the top shell only. If  these are incorrectly installed, no oil will flow to the connecting rods or  main rods, which will result in instant engine failure Replacement bearings should be of a quality as good as or better  than that of the original bearings. The replacement bearings must  also have the same oil holes and grooves.  Modified engines have more demanding bearing requirements and  therefore usually require a higher­quality bearing to provide  satisfactory service Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Count Your Blessings and Your Pan Bolts! Replacing cam bearings can be relatively straightforward or can involve keeping count of the number of oil pan bolts! For example, Buick-built V-6 engines use different cam bearings depending on the number of bolts used to hold the oil pan to the block • • Fourteen bolts in the oil pan The front bearing is special, but the rest of the bearings are the same Twenty bolts in the oil pan Bearings #1 and #4 use two oil feed holes Bearings #2 and #3 use single oil feed holes Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 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 sleeve­type bushings called full round  bearings or split­type (half­shell) bearings In pushrod engines, the cam  bearings are installed in the  block.  Figure 29–75 Cam-in-block engines support the camshaft with sleeve-type bearings Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 29–76 Camshaft bearings must be installed correctly so that oil passages are not blocked Replace the cam bearings when  main bearings are replaced.  The replacement cam bearings  must have correct outside  diameter to fit snugly in the  cam bearing bores of the block They must have the correct oil  holes and be positioned correctly.  Cam bearings must also have the  proper inside diameter to fit the  camshaft bearing journals Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 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 felt­tip 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 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Camshaft bearings used on  overhead camshaft engines may be either full round or split depending on engine  design.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Figure 29–77 Some overhead camshaft engines use split bearing inserts 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Do No Harm All engine parts should be stored in a safe location to help avoid damage prior to being installed in an engine All camshafts and crankshafts should be stored vertically to avoid causing bending or warpage of these parts that could cause difficulty when the engine is being assembled Figure 29–78 Crankshafts should be stored vertically to prevent possible damage or warpage This clever bench-mounted tray for crankshafts not only provides a safe place to store crankshafts but it is out-of-the-way and cannot be accidentally tipped Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY Engine blocks are either cast iron or aluminum Cores are used inside a mold to form water jackets and cylinder  bores. After the cast iron has cooled, the block is shaken, which  breaks up the cores so they fall out of openings in the side of  the block. Core plugs are used to fill the holes The block deck is the surface to which the cylinder head  attaches. This surface must be flat and true for proper engine  operation All bolt holes should be chamfered and cleaned with a thread  chaser before assembly 13 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Forged crankshafts have a wide separation line Cast crankshafts have a narrow mold parting line Even­firing 90­degree V­6 engines require that the crankshaft  be splayed to allow for even firing Lubrication to the main bearings is fed through the main oil  gallery in the block. Oil for the rod bearings comes from  holes in the crankshaft drilled between the main journal and  the rod journal 13 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) A vibration damper, also known as a harmonic balancer, is  used to dampen harmful twisting vibrations of the crankshaft 10 Most engines are internally balanced. This means that the  crankshafts and vibration damper are both balanced. Other  engines use the vibration damper to balance the crankshaft  and are called externally balanced engines 11 Most crankshafts can be reground to be 0.010, 0.020, or 0.030  inch undersize 14 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) 12 Most engine bearings are constructed with a steel shell for  strength and are covered with a copper­lead alloy. Many  bearings also have a thin overlay of babbitt 13 Bearings should have spread and crush to keep them from  spinning when the crankshaft rotates Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 14 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 14 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458