AutoZone 2005 Acura TL 3.2L VTEC SOHC 6cyl | Repair Guides | Engine & Engine Overhaul | Engine & Engine Overhaul | Pistons And Connecting Rods | AutoZone.com

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    Ford Pick-ups and Broncos 1987-1996 Repair Guide

    Pistons and Connecting Rods

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    REMOVAL



    See Figures 1, 2, 3, 4, 5, 6 and 7



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    Fig. Fig. 1: Place rubber hose over the rod studs to protect the crankshaft and cylinders from damage



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    Fig. Fig. 2: Carefully tap the piston out of the bore using a wooden dowel



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    Fig. Fig. 3: Use a ring expander tool to remove the piston rings



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    Fig. Fig. 4: Make connecting rod bolt guides out of rubber tubing; these also protect the cylinder walls and crankshaft journal from scratches



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    Fig. Fig. 5: Push the piston assembly out with a hammer handle



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    Fig. Fig. 6: Match the connecting rods to their caps with a scribe mark for reassembly



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    Fig. Fig. 7: Number each rod and cap with its cylinder number for correct assembly

    4.9L Engine
    1. Drain the cooling system and the crankcase.
    2.  


    CAUTION
    The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

    1. Remove the cylinder head.
    2.  
    3. Remove the oil pan, the oil pump inlet tube and the oil pump.
    4.  
    5. Turn the crankshaft until the piston to be removed is at the bottom of its travel and place a cloth on the piston head to collect filings. Using a ridge reaming tool, remove any ridge of carbon or any other deposit from the upper cylinder walls where piston travel ends. Do not cut into the piston ring travel area more than 1 / 32 in. (0.8mm) while removing the ridge.
    6.  
    7. Mark all of the connecting rod caps so that they can be reinstalled in the original positions from which they are removed and remove the connecting rod bearing cap. Also identify the piston assemblies as they, too, must be reinstalled in the same cylinder from which removed.
    8.  
    9. With the bearing caps removed, the connecting rod bearing bolts are potentially damaging to the cylinder walls during removal. To guard against cylinder wall damage, install 4 in. (101.6mm) or 5 in. (127mm) lengths of 3 / 8 in. (9.5mm) rubber tubing onto the connecting rod bolts. These will also protect the crankshaft journal from scratches when the connecting rod is installed and will serve as a guide for the rod.
    10.  
    11. Squirt some clean engine oil into each cylinder before removing the pistons. Using a wooden hammer handle, push the connecting rod and piston assembly out of the top of the cylinder (pushing from the bottom of the rod). Be careful to avoid damaging both the crank journal and the cylinder wall when removing the rod and piston assembly.
    12.  

    5.0L, 5.8L, 6.9L, 7.3L and 7.5L Engines
    1. Drain the cooling system and the crankcase.
    2.  


    CAUTION
    The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

    1. Remove the intake manifold.
    2.  
    3. Remove the cylinder heads.
    4.  
    5. Remove the oil pan.
    6.  
    7. Remove the oil pump.
    8.  
    9. Turn the crankshaft until the piston to be removed is at the bottom of its travel, then place a cloth on the piston head to collect filings.
    10.  
    11. Remove any ridge of deposits at the end of the piston travel from the upper cylinder bore, using a ridge reaming tool. Do not cut into the piston ring travel area more than 3 / 8 in. (0.8mm) when removing the ridge.
    12.  
    13. Make sure that all of the connecting rod bearing caps can be identified, so they will be reinstalled in their original positions.
    14.  
    15. Turn the crankshaft until the connecting rod that is to be removed is at the bottom of its stroke and remove the connecting rod nuts and bearing cap.
    16.  
    17. With the bearing caps removed, the connecting rod bearing bolts are potentially damaging to the cylinder walls during removal. To guard against cylinder wall damage, install four or five inch lengths of 3 / 8 in. (0.8mm) rubber tubing onto the connecting rod bolts. These will also protect the crankshaft journal from scratches when the connecting rod is installed and will serve as a guide for the rod.
    18.  
    19. Squirt some clean engine oil into each cylinder before removing the piston assemblies. Using a wooden hammer handle, push the connecting rod and piston assembly out of the top of the cylinder (pushing from the bottom of the rod). Be careful to avoid damaging both the crank journal and the cylinder wall when removing the rod and piston assembly.
    20.  
    21. Remove the bearing inserts from the connecting rod and cap if the bearings are to be replace and place the cap onto the piston/rod assembly from which it was removed.
    22.  

    CLEANING AND INSPECTION



    Piston Assembly

    See Figures 8, 9, 10 and 11



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    Fig. Fig. 8: Clean the piston grooves using a ring groove cleaner



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    Fig. Fig. 9: You can use a piece of an old ring to clean the piston grooves, BUT be careful, the ring is sharp



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    Fig. Fig. 10: A telescoping gauge may be used to measure the cylinder bore diameter



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    Fig. Fig. 11: Measure the piston's outer diameter using a micrometer

    A piston ring expander is necessary for removing the piston rings without damaging them; any other method (screwdriver blades, pliers, etc.) usually results in the rings being bent, scratched or distorted, or the piston itself being damaged. When the rings are removed, clean the ring grooves using an appropriate ring groove cleaning tool, using care not to cut too deeply. Thoroughly clean all carbon and varnish from the piston with solvent.


    WARNING
    Do not use a wire brush or caustic solvent (acids, etc.) on pistons.

    Inspect the pistons for scuffing, scoring, cracks, pitting, or excessive ring groove wear. If these are evident, the piston must be replaced.

    Cylinder honing and/or boring should be performed by a reputable, professional mechanic with the proper equipment. In some cases, clean-up honing can be done with the cylinder block in the car, but most excessive honing and all cylinder boring must be done with the block stripped and removed from the car.

    The piston should also be checked in relation to the cylinder diameter. Using a telescoping gauge and micrometer, or a dial gauge, measure the cylinder bore diameter perpendicular (90 percent) to the piston pin, 2 1 / 2 in. (64mm) below the cylinder block deck (surface where the block mates with the heads). Then, with the micrometer, measure the piston, perpendicular to its wrist pin on the skirt. the difference between the two measurements is the piston clearance. If the clearance is within specifications or slightly below (after the cylinders have been bored or honed), finish honing is all that is necessary. If the clearance is excessive, try to obtain a slightly larger piston to bring clearance to within specifications. If this is not possible, obtain the first oversize piston and hone (or if necessary, bore) the cylinder to size. Generally, if the cylinder bore is tapered 0.005 in. (0.127mm) or more or is out-of-round 0.003 in. (0.076mm) or more, it is advisable to rebore for the smallest possible oversize piston and rings.

    After measuring, mark pistons with an indelible felt tip pen for reference and for assembly.

    Before honing the diesel cylinders, the piston oil cooling jets must be removed. this procedure should be handled by a diesel specialist, as special tools are needed. Jets cannot be reused; new jets should be fitted.

    Rod Bearings

    See Figures 12, 13 and 14



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    Fig. Fig. 12: 5.0L and 5.8L engine piston and rod assemblies



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    Fig. Fig. 13: 4.9L engine rod and piston assembly



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    Fig. Fig. 14: 7.5L engine piston and rod installation

    Connecting rod bearings for the engines covered in this guide consist of two halves or shells which are interchangeable in the rod and cap. When the shells are placed in position, the ends extend slightly beyond the rod and cap surfaces so that when the rod bolts are torqued the shells will be clamped tightly in place to insure positive seating and to prevent turning. A tang holds the shells in place.

    The ends of the bearing shells must never be filed flush with the mating surfaces of the rod and cap.

    If a rod bearing becomes noisy or is worn so that its clearance on the crank journal is sloppy, a new bearing of the correct undersize must be selected and installed since there is a provision for adjustment.


    WARNING
    Under no circumstances should the rod end or cap be filed to adjust the bearing clearance, nor should shims of any kind be used.

    Inspect the rod bearings while the rod assemblies are out of the engine. If the shells are scored or show flaking, they should be replaced. If they are in good shape, check for proper clearance on the crank journal (see below). Any scoring or ridges on the crank journal means the crankshaft must be reground and fitted with undersized bearings, or replaced.

    Measuring the Old Pistons

    See Figures 15, 16, 17, 18, 19, 20, 21, 22 and 23



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    Fig. Fig. 15: Cylinder bore measuring points. Take top measurement 1/2 in. (13mm) below top of block deck, bottom measurement 1/2 in. (13mm) above top of piston when piston is at BDC



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    Fig. Fig. 16: Measuring the cylinder bore with a dial gauge



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    Fig. Fig. 17: Proper cylinder bore cross-hatching after honing



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    Fig. Fig. 18: A diesel V8 engine cross-section



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    Fig. Fig. 19: Diesel piston ring identification



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    Fig. Fig. 20: Cylinder bore measurements



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    Fig. Fig. 21: Cylinder bore micrometer



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    Fig. Fig. 22: Check the ring side clearance



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    Fig. Fig. 23: Check piston diameter at these points with a micrometer

    Check used piston-to-cylinder bore clearance as follows:

    1. Measure the cylinder bore diameter with a telescope gauge.
    2.  
    3. Measure the piston diameter. When measuring the pistons for size or taper, measurements must be made with the piston pin removed.
    4.  
    5. Subtract the piston diameter from the cylinder bore diameter to determine piston-to-bore clearance.
    6.  
    7. Compare the piston-to-bore clearances obtained with those clearances recommended. Determine if the piston-to-bore clearance is in the acceptable range.
    8.  
    9. When measuring taper, the largest reading must be at the bottom of the skirt.
    10.  

    Selecting New Pistons
    1. If the used piston is not acceptable, check the service piston size and determine if a new piston can be selected. Service pistons are available in standard, high limit and standard oversize.
    2.  
    3. If the cylinder bore must be reconditioned, measure the new piston diameter, then hone the cylinder bore to obtain the preferred clearance.
    4.  
    5. Select a new piston and mark the piston to identify the cylinder for which it was fitted. On some vehicles, oversize pistons may be found. These pistons will be 0.010 in. (0.254mm) oversize.
    6.  

    CYLINDER HONING



    See Figures 24, 25, 26 and 27



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    Fig. Fig. 24: Removing cylinder glazing using a flexible hone



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    Fig. Fig. 25: A solid hone can also be used to cross-hatch the cylinder bore



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    Fig. Fig. 26: As with a ball hone, work the hone carefully up and down the bore to achieve the desired results



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    Fig. Fig. 27: A properly cross-hatched cylinder bore

    This procedure assumes any carbon ridge has already been removed with a suitable ridge reamer during piston removal.

    1. When cylinders are being honed, follow the manufacturer's recommendations for the use of the hone.
    2.  
    3. Occasionally, during the honing operation, the cylinder bore should be thoroughly cleaned and the selected piston checked for correct fit.
    4.  
    5. When finish-honing a cylinder bore, the hone should be moved up and down at a sufficient speed to obtain a very fine uniform surface finish in a cross-hatch pattern of approximately 45-65° included angle. The finish marks should be clean but not sharp, free from embedded particles and torn or folded metal.
    6.  
    7. Permanently mark the piston for the cylinder to which it has been fitted and proceed to hone the remaining cylinders.
    8.  


    WARNING
    Handle the pistons with care. Do not attempt to force the pistons through the cylinders until the cylinders have been honed to the correct size. Pistons can be distorted through careless handling.

    1. Thoroughly clean the bores with hot water and detergent. Scrub well with a stiff bristle brush and rinse thoroughly with hot water. It is extremely essential that a good cleaning operation be performed. If any of the abrasive material is allowed to remain in the cylinder bores, it will rapidly wear the new rings and cylinder bores. The bores should be swabbed several times with light engine oil and a clean cloth and then wiped with a clean dry cloth. CYLINDERS SHOULD NOT BE CLEANED WITH KEROSENE OR GASOLINE! Clean the remainder of the cylinder block to remove the excess material spread during the honing operation.
    2.  

    PISTON PIN REPLACEMENT



    See Figures 28 and 29



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    Fig. Fig. 28: Use needle-nose or snapring pliers to remove the piston pin clips



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    Fig. Fig. 29: Press the wrist pins in and out with an arbor press. This applies to all engines covered in this information

    All of the Ford gasoline engines covered in this guide utilize pressed-in wrist pins, which can only be removed by an arbor press. The diesel pistons are removed in the same way, only the pistons are heated before the wrist pins are pressed out. On both gasoline and diesel engines, the piston/connecting rod assemblies should be taken to an engine specialist or qualified machinist for piston removal and installation.

    PISTON RING REPLACEMENT



    Piston Ring End-Gap

    See Figures 30, 31, 32 and 33



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    Fig. Fig. 30: Check piston ring end gap with a feeler gauge, with the ring positioned in the cylinder, one inch below the deck of the block



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    Fig. Fig. 31: Proper spacing of the piston ring gaps around the circumference of the piston, for gasoline engines



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    Fig. Fig. 32: Diesel piston ring spacing



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    Fig. Fig. 33: Most rings are marked to show which side should face upward

    Piston ring end gap should be checked while the rings are removed from the pistons. Incorrect end gap indicates that the wrong size rings are being used; ring breakage could occur.


    WARNING
    Do not file moly or chromed rings.

    Compress the piston rings to be used in a cylinder, one at a time, into that cylinder. Squirt clean oil into the cylinder, so that the rings and the top 2 in. (51mm) of cylinder wall are coated. Using an inverted piston, press the rings approximately 1 in. (25mm) below the deck of the block (on diesels, measure ring gap clearance with the ring positioned at the bottom of ring travel in the bore). Measure the ring end gap with the feeler gauge and compare to the Ring Gap chart in this section. Carefully pull the ring out of the cylinder and file the ends squarely with a fine file to obtain the proper clearance.

    Piston Ring Side Clearance Check and Installation

    Check the pistons to see that the ring grooves and oil return holes have been properly cleaned. Slide a piston ring into its groove and check the side clearance with a feeler gauge. On gasoline engines, make sure you insert the gauge between the ring and its lower land (lower edge of the groove), because any wear that occurs forms a step at the inner portion of the lower land. On diesels, insert the gauge between the ring and the upper land. If the piston grooves have worn to the extend that relatively high steps exist on the lower land, the piston grooves have worn to the extent that relatively high steps exist on the lower land, the piston should be replaced, because these will interfere with the operation of the new rings and ring clearance will be excessive. Piston rings are not furnished in oversize widths to compensate for ring groove wear.

    Install the rings on the piston, lowest ring first, using a piston ring expander. There is a high risk of breaking or distorting the rings, or scratching the piston, if the rings are installed by hand or other means.

    Position the rings on the piston as illustrated; spacing of the various piston ring gaps is crucial to proper oil retention and even cylinder wear. When installing new rings, refer to the installation diagram furnished with the new parts.

    ROD BEARING REPLACEMENT



    See Figures 34, 35, 36 and 37



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    Fig. Fig. 34: Check the rod bearing clearance with Plastigage® or equivalent



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    Fig. Fig. 35: Check the connecting rod side clearance with a feeler gauge. Use a small pry bar to spread the connecting rods



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    Fig. Fig. 36: Apply a strip of gauging material to the bearing journal, then install and torque the cap



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    Fig. Fig. 37: After the cap is removed again, use the scale supplied with the gauge material to check clearances

    Make sure connecting rods and their caps are kept together and that the caps are installed in the proper direction.

    Replacement bearings are available in standard size and in undersizes for reground crankshaft. Connecting rod-to-crankshaft bearing clearance is checked using Plastigage® at either the top or bottom of each crank journal. the Plastigage® has a range of 0 to 0.003 in. (0.076mm).

    1. Remove the rod cap with the bearing shell. Completely clean the bearing shell and the crank journal and blow any oil from the oil hole in the crankshaft.
    2.  

    The journal surfaces and bearing shells must be completely free of oil, because Plastigage® is soluble in oil.

    1. Place a strip of Plastigage® lengthwise along the bottom center of the lower bearing shell, then install the cap with shell and tighten the bolt or nuts to specification. DO NOT TURN the crankshaft with the Plastigage® installed in the bearing.
    2.  
    3. Remove the bearing cap with the shell. The flattened Plastigage® will be found sticking to either the bearing shell or crank journal. Do not remove it yet.
    4.  
    5. Use the printed scale on the Plastigage® envelope to measure the flattened material at its widest point. The number within the scale which most closely corresponds to the width of the Plastigage® indicated bearing clearance in thousandths of an inch.
    6.  
    7. Check the specifications chart in this section for the desired clearance. It is advisable to install a new bearing if clearance exceeds 0.003 in. (0.076mm); however, if the bearing is in good condition and is not being checked because of bearing noise, bearing replacement is not necessary.
    8.  
    9. If you are installing new bearings, try a standard size, then each undersize in order until one is found that is within the specified limits when checked for clearance with Plastigage® . Each under size has its size stamped on it.
    10.  
    11. When the proper size shell is found, clean off the Plastigage® material from the shell, oil the bearing thoroughly, reinstall the cap with its shell and tighten the rod bolt nuts to specification.
    12.  

    With the proper bearing selected and the nuts torqued, it should be possible to move the connecting rod back and forth freely on the crank journal as allowed by the specified connecting rod end clearance. If the rod cannot be moved, either the rod bearing is too far undersize or the rod is misaligned.

    INSTALLATION



    See Figures 38, 39, 40 and 41



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    Fig. Fig. 38: Most pistons are marked to indicate positioning in the engine (usually a mark means the side facing front)



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    Fig. Fig. 39: Installing the piston into the block using a ring compressor and the handle of a hammer



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    Fig. Fig. 40: The notch on the side of the bearing cap matches the groove on the bearing insert



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    Fig. Fig. 41: Checking the ring-to-ring groove clearance

    4.9L Engine
    1. Before installing the piston/connecting rod assembly, be sure to clean all gasket mating surfaces, oil the pistons, piston rings and the cylinder walls with light engine oil.
    2.  
    3. Be sure to install the pistons in the cylinders from which they were removed. The connecting rod and bearing caps are numbered from 1 to 6 beginning at the front of the engine. The numbers on the connecting rod and bearing cap must be on the same side when installed in the cylinder bore. If a connecting rod is ever transposed from one engine or cylinder to another, new bearings should be fitted and the connecting rod should be numbered to correspond with the new cylinder number. The notch on the piston head goes toward the front of the engine.
    4.  
    5. Make sure the ring gaps are properly spaced around the circumference of the piston. Make sure rubber hose lengths are fitted to the rod bolts. Fit a piston ring compressor around the piston and slide the piston and connecting rod assembly down into the cylinder bore, pushing it in with the wooden hammer handle. Push the piston down until it is only slightly below the top of the cylinder bore. Guide the connecting rods onto the crankshaft bearing journals carefully, using the rubber hose lengths, to avoid damaging the crankshaft.
    6.  
    7. Check the bearing clearance of all the rod bearings, fitting them to the crankshaft bearing journals.
    8.  
    9. After the bearings have been fitted, apply a light coating of engine oil to the journals and bearings.
    10.  
    11. Turn the crankshaft until the appropriate bearing journal is at the bottom of its stroke, then push the piston assembly all the way down until the connecting rod bearing seats on the crankshaft journal. Be careful not to allow the bearing cap screws to strike the crankshaft bearing journals and damage them.
    12.  
    13. After the piston and connecting rod assemblies have been installed, check the connecting rod side clearance on each crankshaft journal.
    14.  
    15. Prime and install the oil pump and the oil pump intake tube, then install the oil pan.
    16.  
    17. Reassemble the rest of the engine in the reverse order of disassembly.
    18.  

    5.0L, 5.8L, 6.9L, 7.3L and 7.5L Engines

    See Figure 42



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    Fig. Fig. 42: Diesel piston positioning

    1. Install the piston/rod assemblies in the same manner as that for the 6-cylinder engines. See the procedure given for 6-cylinder engines.
    2.  

    The connecting rod and bearing caps are numbered from 1 to 4 in the right bank and from 5 to 8 in the left bank, beginning at the front of the engine. The numbers on the rod and cap must be on the same side when they are installed in the cylinder bore. Also, the largest chamfer at the bearing end of the rod should be positioned toward the crank pin thrust face of the crankshaft and the notch in the head of the piston faces toward the front of the engine.

    1. See the appropriate component procedures to assemble the engine.
    2.  

     
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