Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989

Pistons, Piston Pins, Connecting Rods and Bearings

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REMOVAL



See Figures 1, 16 and 17

Although it is easier and cleaner to work on an engine which has been removed, pistons and connecting rods can be removed with the engine still in the car (after the cylinder head and oil pan have been removed). Engine removal is required, however, if the crankshaft will also be removed.

All parts must be retained in order-including the bearings and caps. Mark the caps for installation in the same position in both directions, if they are not already marked. Note that on all engines except those used in the 1983-89 626/MX-6 and the 1986-89 323, thrust bearings are at the rear main. This main bearing cap must be removed with a puller. The 1983-87 2.0L engines, including the diesel, have them on the center main, and the 1.6L turbo and non-turbo engines have them on the No. 4 main. Be careful not to lose or mix up the thrust washers. On the 1988-89 626 and MX-6, crankshaft thrust is taken up by the center main bearing. On these engines, the thrust washers are integral with the bearing.

When removing the crankshaft, use a stand that permits the engine to be inverted. Remove the engine (or engine/transaxle assembly) as described earlier in this section. If applicable, separate the transaxle from the engine. After removing the flywheel/flexplate, detach the oil pump from the front of the engine. (Refer to these procedures elsewhere in this section.) Invert the engine, then remove the main bearing caps, bearings and crankshaft, as described later in this section.



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Fig. Fig. 1: Loosen the connecting rod nuts until flush with the bolt ends, then gently tap them until the cap is free

  1. If applicable, remove the engine from the vehicle, as previously described in this section, and mount it on a suitable workstand. Otherwise, remove the cylinder head(s) and oil pan, also as previously described.
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  3. Note the position of each piston, connecting rod and connecting rod cap before removal, to ensure reinstallation in the same location. Check the tops of the pistons and the sides of the connecting rods for identifying marks. If no identifying numbers or marks are present, use a number punch set and stamp in the numbers yourself.
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  5. Rotate the crankshaft until the piston to be removed is at the bottom of the cylinder. Inspect the upper area of the cylinder wall for a ridge above the top piston ring. If cylinder wall wear has created a noticeable ridge, it should be removed with a ridge reamer, to prevent damage to the rings during piston removal. For further information on ridge removal, refer to the procedure later in this section.
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WARNING
Be very careful if you are unfamiliar with operating a ridge reamer. It is very easy to remove more cylinder bore material than intended, possibly requiring a cylinder overbore and piston replacement that could have been avoided.

  1. Loosen the connecting rod nuts until they are flush with the ends of the rod bolts. Use a hammer and brass drift or piece of wood to lightly tap on the nuts/bolts until the connecting rod cap comes free of the connecting rod. Remove the nuts, rod cap and lower bearing insert.
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  3. Slip a length of snug fitting rubber hose over each rod bolt, to prevent the bolt threads from damaging the crankshaft during removal.
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  5. Using a hammer handle or piece of wood or plastic, tap the rod and piston upward in the bore until the piston rings clear the cylinder block. Remove the piston and connecting rod assembly from the top of the cylinder bore.
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  7. If applicable, repeat Steps 3-6 for the other pistons.
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CLEANING AND INSPECTION



See Figures 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15

  1. Check the top deck of the block for distortion by running a straightedge along both sides, both ends, and diagonally. Check for distortion exceeding 0.006 in. (0.15mm), (0.004 in./0.10mm on the diesel) by attempting to insert an appropriate size flat feeler gauge between the block deck and the lower edge of the straightedge all along its length, in every direction shown. If distortion exceeds the limit, have the block top deck ground by a competent machine shop or, if distortion is excessive, replace the block.
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Fig. Fig. 2: After removing all head gasket material, check the cylinder block deck for distortion by placing a straightedge along both sides, both ends, and diagonally



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Fig. Fig. 3: A telescoping gauge or inside micrometer may be used to measure the cylinder diameter bore



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Fig. Fig. 4: Measure the diameter of each cylinder at three different depths; also, take three additional readings, perpendicular to the first ones



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Fig. Fig. 5: Measure the piston's outside diameter using a micrometer

Do not attempt to save a diesel cylinder block through grinding! If the distortion exceeds the limit, the block must be replaced. Otherwise, the pistons will hit the valves!

  1. Also inspect the block for cracks or wetness, indicating coolant has leaked through the cracks. If you have any doubt about such problems, you should have the block inspected by the Zyglo®, Magnaflux® or similar process, to ensure it can be reused without risk of leakage. Pressure testing is another means by which the block may be tested for cracks.
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The Zyglo® process coats parts with a fluorescent dye penetrant that is suitable for any material. Magnaflux® is a magnetic process applicable only to ferrous materials.

  1. Measure the diameter of each cylinder at the six locations shown. Subtract the minimum dimension from the maximum dimension. If this difference exceeds 0.0059 in. (0.15mm), or the difference between cylinders exceeds 0.0007 in. (0.01778mm), cylinders must be bored and oversize pistons installed. If boring is required, you should base the amount that you remove on the dimensions of an oversize piston. When one cylinder is bored, all other cylinders must be bored the same amount. Any time this type of machining is done, it should be documented. On the diesel, maximum diameter must not exceed 3.39 in. (86mm), and the difference between cylinder bores must not exceed 0.009 in. (0.23mm). Wall scoring or signs of piston seizure also mean cylinders must be rebored.
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Even if only one cylinder is damaged, all must be bored and the same oversize pistons installed (for balance). Pistons are offered in oversizes of 0.010 in. (0.254mm) and 0.020 in. (0.508mm) for most engines.

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Fig. Fig. 6: Measure piston diameter at the position shown-gasoline engines



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Fig. Fig. 7: Measure piston diameter at the position shown-diesel engine



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Fig. Fig. 8: Use a ring expander tool to remove the piston rings



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Fig. Fig. 9: Clean the piston grooves using a ring groove cleaner ...



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Fig. Fig. 10: ... or part of a broken piston ring. Be careful, since the ring is sharp

  1. On 2.0L (Codes FE and RF), 2.2L and 3.0L engines, test the oscillation torque of the rod by holding the piston in a horizontal position, and raising the rod until it touches the piston skirt, then releasing it. The rod should descend freely; otherwise, replace the piston and/or piston pin. If replacement is indicated, press the piston pin out with tools designed for this purpose.
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This procedure requires the use of a hydraulic press that produces and measures total pressures of 1,100-3,300 lbs. (500-1,500 kg). You may wish to remove the piston/rod assemblies yourself and have the pressing operations performed at a competent automotive machine shop.

  1. On gasoline engines, other than the 1.3L engine, if the pressure required to press the pin from the piston is less than 1,100 lbs. (500 kg), replace the piston pin or the connecting rod.
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  3. Measure piston diameter in the thrust direction, below the bottom of the oil ring groove and 90 degrees from the piston pin, as shown in the illustration. On the diesel, measure it 0.75 in. (19mm) above the bottom edge of the piston skirt. This dimension must compare with cylinder diameter so as to produce piston-to-cylinder clearance that is within specifications. If clearance exceeds the maximum wear specification, all cylinders must be bored and appropriate oversize pistons must be installed. If the clearance is within specification, only light finish honing is required.
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  5. Using a ring expander tool, as illustrated, remove the piston rings. The various rings on each piston are not identical. Be careful not to mix them up, in case they may be reused.
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If the piston is to be replaced, also install new piston rings.

  1. Clean the pistons thoroughly with a suitable solvent or in a dip tank. All the ring lands must be free and clear of any carbon deposits. Use a ring groove cleaning tool or a broken piston ring, which allows you to reach the innermost part of the land. DO NOT use a file or wire brush to clean the piston. Inspect the rings for damage or cracks and measure side clearance, as shown, using a new piston ring. Also measure end-gap, as shown, with the rings near the bottom of the cylinder-below the area of ring wear. This should be done even for new rings.
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  3. Install the connecting rods in a jig designed to test straightness and check that the bend or twist does not exceed 0.0016 in. (0.04mm) per 3.94 in. (100mm) of length on all 1978-88 gasoline engines. On 1989 1.6L engines, the bend or twist should not exceed 0.0078 in. (0.20mm) per 3.94 in. (100mm), and on 1989 2.2L and 3.0L engines, the limit is 0.0024 in. (0.06mm). On the 1985 2.0L diesel engine, bend or twist should not exceed 0.006 in. (0.15mm) per 3.94 in. (100mm) of length.
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  5. Measure the piston pin diameter and the piston pin hole diameter each in eight places, as illustrated. Compare the readings and replace any out-of-round components. Also, if pin-to-hole clearance is beyond the specified limit, replace the piston and/or piston pin.
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Fig. Fig. 11: Check the piston ring side clearance using a new ring and a feeler gauge



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Fig. Fig. 12: Measure ring end-gap by placing the ring inside the cylinder, in the area of ring-induced wear. Use an inverted piston to keep the ring from cocking



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Fig. Fig. 13: Use an inside caliper to measure the piston pin hole diameter in eight places



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Fig. Fig. 14: Use a micrometer to take eight measurements of a piston pin



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Fig. Fig. 15: When replacing connecting rod bushings on the diesel, align the bushing and rod oil holes prior to pressing in the bushing. If necessary, ream the new bushing to provide the proper clearance

  1. On diesel engines, the upper ends of the connecting rods are bushed. Measure the outside diameter of the piston pin with a micrometer; use an inside micrometer to measure the inside diameter of the bushing. Then, subtract the smaller figure from the larger. The standard inner diameter of the bushing is 0.9846-0.9854 in. (25.01-25.03mm), and the clearance limit between the two is 0.002 in. (0.05mm). If the clearance exceeds this figure, press the bushing out of the rod and replace it as follows:
    1. Press the bushing out by supporting the upper rod end on a block with a suitable hole in it (for passage of the bushing downward). Place a pipe of 1.06-1.08 in. (27.0-27.4mm) diameter under the press, squarely aligned with the end of the pin (NOT touching the rod). Press the bushing out.
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    3. Thoroughly coat the outer bore of the new bushing and the inner bore of the rod with clean engine oil. Precisely align the oil holes of the bushing and rod bore. Then, press in the new bushing until its edges are aligned with the sides of the rod and the oil holes are precisely lined up.
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    5. Add the minimum required piston pin-to-rod clearance to the actual pin diameter. Then, using a spiral expansion reamer, repeatedly enlarge and measure the inside diameter of the bushing until clearance is within specification.
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RIDGE REMOVAL AND HONING



See Figures 16, 17, 18 and 19

  1. Before the piston is removed from the cylinder, check for a ridge at the top of the cylinder bore. This ridge occurs because the piston ring does not travel all the way to the top of the bore, thereby leaving an unused portion of cylinder bore.
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  3. In order to see the extent of the ridge more clearly, clean away any carbon buildup at the top of the cylinder with sandpaper. If the ridge is slight, it will be safe to remove the pistons without damaging the rings or piston ring lands. If the ridge is severe, and easily catches your fingernail, it will have to be removed using a ridge reamer.
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Fig. Fig. 16: Before extracting the pistons, remove any ridges from the upper portions of the cylinder walls



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Fig. Fig. 17: Removing the ridge from a cylinder bore with a ridge reamer



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Fig. Fig. 18: Using a ball-type cylinder hone is an easy way to finish the cylinder bore



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Fig. Fig. 19: A properly cross-hatched cylinder bore

A severe ridge is an indication of excessive bore wear. Before removing the piston, check the cylinder bore diameter with a bore gauge, as explained in the piston and connecting rod cleaning and inspection procedure. Compare your measurement with specification. If the bore is excessively worn, all cylinders will have to bored (to maintain balance), then oversize pistons and rings must be installed.

  1. Before reaming the ridge, cover the piston top with a rag to minimize the amount of metal which enters the cylinder. Install the ridge removal tool in the top of the cylinder bore, then carefully follow the manufacturer's operating instructions. Only take off the amount of material necessary to remove the ridge. Clean up all metal shavings before attempting to remove the piston/rod assembly.
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WARNING
Be very careful if you are unfamiliar with operating a ridge reamer. It is very easy to remove more cylinder bore material than you want, possibly requiring a cylinder overbore and piston replacement that may not have been necessary.

  1. After the piston and connecting rod assembly have been removed, check the clearances as explained in the piston and connecting rod cleaning and inspection procedure, to determine whether boring and honing or just light honing are required. If boring is necessary, consult an automotive machine shop. If light honing is all that is necessary, proceed to Step 5.
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  3. Honing is best done with the crankshaft removed, to prevent damage to the crankshaft and to make post-honing cleaning easier, since the honing process will scatter metal particles. However, if you do not want to remove the crankshaft, position the connecting rod journal for the cylinder being honed as far away from the bottom of the cylinder bore as possible, and wrap a shop cloth around the journal.
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  5. Honing can be done either with a flexible glaze breaker-type hone or with a rigid hone that has honing stones and guide shoes. The flexible hone removes the least amount of metal, and is especially recommended if your piston-to-cylinder bore clearance is on the loose side. The flexible hone is useful to provide a finish on which the new piston rings will seat. A rigid hone will remove more material than the flexible hone and requires more operator skill.
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  7. Regardless of which type of hone you use, carefully follow the manufacturer's instructions for operation.
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  9. The hone should be moved up and down the bore at sufficient speed to obtain a uniform finish. A rigid hone will provide a definite cross-hatch finish; operate the rigid hone at a speed to obtain a 45-65° included angle in the cross-hatch. The finish marks should be clean, but not sharp, and free from embedded particles and torn or folded metal.
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  11. Periodically during the honing procedure, thoroughly clean the cylinder bore and check the piston-to-bore clearance with the piston for that cylinder.
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  13. After honing is completed, thoroughly wash the cylinder bores and the rest of the engine with hot water and detergent. Scrub the bores well with a stiff bristle brush and rinse thoroughly with hot water. Thorough cleaning is essential, for if any abrasive material is left in the cylinder bore, it will rapidly wear the new rings and the cylinder bore. If any abrasive material is left in the rest of the engine, it will be picked up by the oil and carried throughout the engine, damaging bearings and other parts.
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  15. After the bores are cleaned, wipe them down with a clean cloth coated with light engine oil, to keep them from rusting.
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PISTON ASSEMBLY



See Figures 20, 21, 22, 23, 24, 25 and 26

  1. If applicable, pistons and rods must be assembled (piston pins installed) with rods facing in the proper direction. With the F mark on the piston facing you, turn the connecting rod so the oil hole which lubricates the cylinder is on the left. (This also applies to the diesel.) On 1979-82 626 engines, the rod is assembled with the connecting rod bolt heads pointing to the right, as shown. The piston pin (and other related parts) must be thoroughly lubricated with clean engine oil and pressed in from the F mark side. On the 1.3L engine, heat the piston slightly if the pin is a tight fit, press it into the piston, and install new circlips. On the diesel, heat the piston to 122°-168°F (50°C-76°C). Then, install the connecting rod in the proper direction into the piston, slide the pin into position, and lock the pin with circlips.
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Fig. Fig. 20: Piston and connecting rod assembly-except 1979-82 2.0L (Code MA) engine



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Fig. Fig. 21: On 1979-82 2.0L (Code MA) engines, the connecting rod bolt heads angle to the right



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Fig. Fig. 22: Installing the oil control ring's upper rail



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Fig. Fig. 23: Most rings are marked to show which side faces upward



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Fig. Fig. 24: Stagger the positions of the ring gaps around the piston as shown



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Fig. Fig. 25: Using the piston pin as a baseline, upper and lower compression ring openings should each be offset 30° in opposite directions. The oil control ring's upper and lower rails should also be offset



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Fig. Fig. 26: Install rings for the 2.0L diesel engine as shown. Make sure that the "R" or "RN" marks face upward

On gasoline engines, other than the 1.3L engine, this job requires special tools and a press that can apply and measure 1,100-3,300 lbs. (500-1,500 kg) of force. If it requires less than 1,100 lbs. (500 kg) to insert the pin, the pin or connecting rod must be replaced.

  1. On the 2.0L (Codes FE and RF), 2.2L and 3.0L engines, the completed assembly must pass the connecting rod oscillation torque test previously described. If the rod does not descend freely, replace the piston and/or piston pin.
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  3. Install the three-piece oil control ring with its rails and grooves thoroughly lubricated. Start with the oil control ring spacer (expander). Next, install the oil control upper rail by inserting one edge between the groove and spacer, and holding it in place with your thumb. Then, run your other thumb along the edge of the rail to work it into the groove. Install the lower rail similarly. Check that both rails are expanded by the spacer tangs, so that they turn smoothly in both directions.
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On many engines, the upper and lower rails are identical, and can be installed with either face upward.

  1. Install the lower (second) compression ring, followed by the upper ring, with R or RN markings facing upward. Use a ring expander, but open the rings as little as possible. When the rings are installed, oil them and stagger their gaps as shown in the illustrations, to prevent excessive oil consumption and loss of compression.
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INSTALLATION



See Figures 27, 28, 29, 30, 31 and 32

  1. Make sure the cylinder bore and shaft journal are clean.
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  3. Position the crankshaft journal at its furthest position away from the bottom of the cylinder bore.
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  5. Coat the cylinder bore with light engine oil.
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  7. Make sure the rod bearing shells are correctly installed. Slip a length of snug rubber hose over each rod bolt, to prevent the threads from damaging the shaft during installation.
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  9. Check that the piston rings are installed with the end-gaps properly positioned. Install a ring compressor over the piston and rings, then compress the rings into their grooves. (Follow the ring compressor manufacturer's instructions.)
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  11. Place the piston and connecting rod assembly into the cylinder bore. (If more than one piston was removed, make sure the assembly is in the proper bore.) Also, make sure that the piston and connecting rod are facing in the correct direction. Most pistons have an arrow or notch on the top of the piston, or the letter F appears somewhere on the piston, to indicate the side which faces the front of the engine.
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  13. Check that the compressor is seated squarely on the block deck surface. If the compressor is not seated squarely, a ring could pop out from beneath the compressor and catch on the deck as the piston is tapped into its bore. Also, make sure the connecting rod is not hung up on the crankshaft counterweights, and is in position to engage the crankshaft.
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  15. Tap the piston slowly into the bore, making sure the ring compressor remains squarely against the block. When the piston is completely in its bore, remove the compressor.
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  17. Pull the connecting rod onto the crank journal, then remove the rubber hoses. Verify proper bearing fit by temporarily installing the rod cap with dry bearings and a Plastigage® insert. Check that the insert is not seated on an oil hole, and be sure the cap mark is aligned with the rod mark. Torque the connecting rod nuts to specification. Unfasten the connecting rod nuts, then remove the cap and the Plastigage®. Compare the insert's dimensions with specifications.
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Fig. Fig. 27: Most pistons are marked to indicate positioning in the engine. Usually, a mark indicates the side facing front



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Fig. Fig. 28: Installing a piston into the block using a ring compressor and hammer handle



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Fig. Fig. 29: The notch on the side of the connecting rod matches the groove on the bearing insert



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Fig. Fig. 30: Apply a strip of gauging material to the bearing journal, before installing the cap



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Fig. Fig. 31: Install the connecting rod cap with matchmarks on the cap and rod aligned



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Fig. Fig. 32: After removing the cap, compare the gauging material dimensions with clearance specifications

Even when the crankpin journal diameter surpasses minimum specifications, it is possible that bearing clearance is excessive. If the crankpin bearing oil clearance exceeds the maximum limit of 0.0039 in. (0.10mm) for gasoline engines, or 0.0031 in. (0.08mm) on the diesel, the journals must be machined and undersize bearings installed. If this work is necessary, it should be coordinated with a check of the crankshaft main bearings and journals, as well as end-play, as described later in this section.

  1. After verifying proper bearing fit, coat the crankshaft journal and connecting rod bearings with engine assembly lube or clean engine oil. Attach the connecting rod cap, then lightly oil the bolt threads and torque the nuts. Make sure the crankshaft rotates freely after each rod cap in torqued.
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  3. Measure the clearance between the sides of the connecting rod itself (not the cap) and the crankshaft, with a feeler gauge. If the clearance is below minimum specifications, the connecting rod will have to be removed and machined. If the clearance is excessive, substitute an unworn rod and recheck. If clearance is still excessive, the crankshaft must be welded and reground, or replaced.
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  5. If applicable, repeat Steps 1-11 for the other pistons.
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