Nissan Pick-ups and Pathfinder 1970-1988

Cylinder Head

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REMOVAL & INSTALLATION



L16, L18 and L20B Engines

See Figures 5, 6, 7, 8, 9, 10 and 11

  1. Crank the engine until the No. 1 piston is at TDC of the compression stroke and disconnect the negative battery cable, drain the cooling system, and remove the air cleaner and attending hoses.
  2.  
  3. Remove the alternator.
  4.  
  5. If equipped with air conditioning, unbolt the compressor and move it aside onto the fender. Do not detach any of the compressor lines; the escaping refrigerant will freeze any surface it contacts, including your skin.
  6.  
  7. Disconnect the carburetor throttle linkage, the fuel line and any other vacuum lines or electrical leads, and remove the carburetor.
  8.  
  9. Disconnect the exhaust pipe from the exhaust manifold.
  10.  
  11. Remove the fan and fan pulley.
  12.  
  13. Remove the spark plugs to protect them from damage. Lay the spark plugs aside and out of the way.
  14.  
  15. Remove the cylinder head cover.
  16.  
  17. Remove the water pump.
  18.  
  19. On models with a mechanical fuel pump, remove the pump from the cylinder head.
  20.  
  21. Remove the fuel pump drive cam.
  22.  
  23. Mark the relationship of the camshaft sprocket to the timing chain with paint or chalk. If this is done, it will not be necessary to locate the factory timing marks. Before removing the camshaft sprocket, it will be necessary to wedge the chain in place so that it will not fall down into the front cover. The factory procedure is to wedge the timing chain in place with the wooden wedge. The problem with this is that it may allow the chain tensioner to move out far enough to cock itself against the chain. If this happens, you'll find that the chain won't go back over the sprocket after you've put the sprocket back on. In this case, you'll have to remove the front cover and push the tensioner back. After installing the wedge, unbolt and remove the camshaft sprocket.
  24.  
  25. Loosen and remove the cylinder head bolts, gradually and in the order shown. You will need a 10mm Allen wrench to remove the head bolts. Keep the bolts in order, because they are different sizes. Lift the cylinder head assembly from the engine. Remove the intake and exhaust manifolds as necessary.
  26.  

To install:
  1. Thoroughly clean the cylinder block and head mating surfaces. Check the block and head for flatness before installing the head. Install a new cylinder head gasket. Do not use sealer on the cylinder head gasket of 1973-80 models. Use sealer on all other models.
  2.  
  3. With the crankshaft turned so that the No. 1 piston is at TDC of the compression stroke (if not already done so as mentioned in Step 1), make sure that the camshaft sprocket timing mark and the oblong groove in the camshaft retaining plate are aligned.
  4.  
  5. Place the cylinder head in position on the cylinder block, being careful not to allow any of the valves to come in contact with any of the pistons. Do not rotate the crankshaft or camshaft separately because of possible damage which might occur to the valves.
  6.  
  7. Temporarily tighten the two center right and left cylinder head bolts to 14.5 ft. lbs. (20 Nm).
  8.  
  9. Install the camshaft sprocket together (with the timing chain) to the camshaft. Make sure that the marks you made earlier line up. If the chain will not stretch over the sprocket, the problem lies in the tensioner. See the Timing Chain Removal and Installation for timing procedure, if necessary.
  10.  
  11. Install the cylinder head bolts. Note that there are two sizes of bolts used; the longer bolts are installed on the driver side of the engine with a smaller bolt in the center position. The remaining small bolts are installed on the opposite side of the cylinder.
  12.  
  13. Tighten the cylinder head bolts in three stages on 1973-80 models: first to 29 ft. lbs. (39 Nm), second to 43 ft. lbs. (58 Nm), and lastly to 47-62 ft. lbs. (64-84 Nm). On 1970-72 models, tighten the cylinder head bolts to 36-43 ft. lbs. (49-58 Nm) in three progressive steps. Tighten the cylinder head bolts on all models in the proper sequence.
  14.  
  15. Install the fuel pump assembly, water pump and cylinder head cover.
  16.  
  17. Clean and regap the spark plugs then install plugs into the cylinder head. DO NOT OVER-TORQUE THE SPARK PLUGS!
  18.  
  19. Install the fan pulley and cooling fan. Connect the exhaust pipe to the exhaust manifold.
  20.  
  21. Install the carburetor and connect the carburetor throttle linkage, the fuel line and any other vacuum lines or electrical leads.
  22.  
  23. Install the alternator and its electrical connections. Install the drive belt and adjust the tension.
  24.  
  25. Adjust the valves. Fill the cooling system and then start the engine and run it until it reaches normal operating temperature. Retighten the cylinder head bolts to specifications. Readjust the valves. Retighten the cylinder head bolts again after 600 miles, and readjust the valves at that time.
  26.  



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Fig. Fig. 5: Cylinder head bolt loosening sequence-L16, L18 and L20B engines



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Fig. Fig. 6: Different size cylinder head bolts-L16, L18 and L20B engines



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Fig. Fig. 7: Cylinder head bolt tightening sequence-L16, L18 and L20B engines



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Fig. Fig. 8: Dimensions for fabricating the wooden wedge used in support for the timing chain-L16, L18 and L20B engines (Z-series engine similar)



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Fig. Fig. 9: Removing the camshaft sprocket and chain-L16, L18 and L20B engines



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Fig. Fig. 10: Support the timing chain with a wedge-L16, L18 and L20B engines



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Fig. Fig. 11: Installing the camshaft sprocket-L16, L18 and L20B engines

Z20, Z22, Z24 and Z24i Engines

See Figures 12, 13, 14, 15, 16 and 17

  1. Crank the engine until the No. 1 piston is at TDC of the compression stroke and disconnect the negative battery cable, drain the cooling system, and remove the air cleaner and attending hoses.
  2.  
  3. Remove the alternator.
  4.  
  5. If equipped with air conditioning, unbolt the compressor and move it aside onto the fender. Do not detach any of the compressor lines; the escaping refrigerant will freeze any surface it contacts, including your skin.
  6.  
  7. Disconnect the carburetor throttle linkage, the fuel line and any other vacuum lines or electrical leads, and remove the carburetor.
  8.  
  9. Disconnect the exhaust pipe from the exhaust manifold.
  10.  
  11. Remove the fan and fan pulley.
  12.  
  13. Disconnect the throttle linkage, the air cleaner or its intake hose assembly (fuel injection). Disconnect the fuel line (on fuel injected engines-release fuel pressure) the return fuel line and any other vacuum lines or electrical leads. Remove the carburetor (Z20, Z22 and Z24) to avoid damaging it while removing the head.
  14.  

A good rule of thumb when disconnecting the rather complex engine wiring of today's automobiles is to put a piece of masking tape on the wire or hose and on the connection you removed the wire or hose from, then mark both pieces of tape 1, 2, 3, etc. When replacing wiring, simply match the pieces of tape.

  1. Remove the EGR tube from around the rear of the engine.
  2.  
  3. Remove the exhaust air induction tubes from around the front of the engine and from the exhaust manifold.
  4.  
  5. Unbolt the exhaust manifold from the exhaust pipe. Remove the fuel pump.
  6.  
  7. Remove the intake manifold supports from under the manifold. Remove the PCV valve from around the rear of the engine if necessary.
  8.  
  9. Remove the spark plugs to protect them from damage. Remove the cylinder head cover.
  10.  

The spark plug leads should be marked, however it would be wise to mark them yourself, especially the dual spark plug models.

  1. Mark the relationship of the camshaft sprocket to the timing chain with paint or chalk. If this is done, it will not be necessary to locate the factory timing marks. Before removing the camshaft sprocket, it will be necessary to wedge the chain in place so that it will not fall down into the front cover. The factory procedure is to wedge the timing chain in place with the wooden wedge shown in the illustration. The problem with this procedure is that it may allow the chain tensioner to move out far enough to cock itself against the chain. If this happens, you'll find that the chain won't go back over the sprocket after you've put the sprocket back on. In this case, you'll have to remove the front cover and push the tensioner back. After you've wedged the chain, unbolt the camshaft sprocket and remove it.
  2.  
  3. Working from both ends in, loosen the cylinder head bolts and remove them. Remove the bolts securing the cylinder head to the front cover assembly.
  4.  
  5. Lift the cylinder head off the engine block. It may be necessary to tap the head lightly with a rubber mallet to loosen it.
  6.  

To install:
  1. Thoroughly clean the cylinder block and head surfaces, then check both for warpage.
  2.  
  3. Fit the new head gasket. Don't use sealant. Make sure that no open valves are in the way of raised pistons, and never rotate the crankshaft or camshaft separately because of possible damage which might occur to the valves.
  4.  
  5. Temporarily tighten the two center right and left cylinder head bolts to 14 ft. lbs. (19 Nm).
  6.  
  7. Install the camshaft sprocket together with the timing chain to the camshaft. Make sure the marks you made earlier line up with each other. If you get into trouble, see Timing Chain Removal and Installation for timing procedures.
    1. On the Z24i, confirm that the No. 1 cylinder is set at TDC on its compression stroke. Make sure that the front knock pin is positioned at the upper surface of the camshaft. Set the chain on the camshaft sprocket by aligning each mating mark. Then install the camshaft sprocket to the camshaft and tighten to 87-116 ft. lbs. (118-157 Nm)The camshaft sprocket should be installed by fitting the knock pin of the camshaft into its No. 2 hole. And the No. 2 timing mark must also be used.
    2.  
    3. Apply sealant to the sealing point of the cylinder head and install the rubber plug.
    4.  

  8.  
  9. Install the cylinder head bolts and torque them to 22 ft. lbs. (29 Nm), then 40 ft. lbs. (54 Nm), and then 58 ft. lbs. (78 Nm). Loosen all bolts completely and retighten 22 ft. lbs. (29 Nm), and then to 54-61 ft. lbs. (74-83 Nm); or, if you have an angle torque wrench, give all bolts a final turn of 90-95 degrees. Tighten all bolts gradually, in the order shown.
  10.  
  11. Clean and regap the spark plugs then install them in the cylinder head. DO NOT OVER-TORQUE THE SPARK PLUGS!
  12.  
  13. Install the cylinder head cover with a new gasket.
  14.  
  15. Install the intake manifold supports from under the manifold. Install the PCV valve if it was removed.
  16.  
  17. Connect the exhaust pipe to exhaust manifold. Install the fuel pump.
  18.  
  19. Install the exhaust air induction tubes to the front of the engine or to the exhaust manifold.
  20.  
  21. Install the EGR tube from around the rear of the engine.
  22.  
  23. Install the carburetor (Z20, Z22 and Z24). Connect the throttle linkage, the air cleaner or its intake hose assembly (Z24i). Reconnect the fuel line, the return fuel line and any other vacuum lines or electrical leads.
  24.  
  25. Install the power steering pump if so equipped and correctly adjust the drive belt.
  26.  
  27. Install the air conditioning compressor and correctly adjust the drive belt.
  28.  
  29. Install the alternator mounting bracket and alternator. Engage the electrical connections to the alternator and adjust the drive belt.
  30.  
  31. Reconnect the heater and radiator hoses.
  32.  
  33. Refill the cooling system. Adjust the valves.
  34.  
  35. Start the engine and it until it reaches normal operating temperature, check for the correct coolant level.
  36.  
  37. Check for leaks and roadtest vehicle for proper operation.
  38.  

It is always wise to drain the crankcase oil after the cylinder head has been installed to avoid possible coolant contamination of the old oil.



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Fig. Fig. 12: Cylinder head bolt loosening sequence-Z20, Z22, Z24 and Z24i engines



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Fig. Fig. 13: Cylinder head bolt tightening sequence-Z20, Z22, Z24 and Z24i engines



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Fig. Fig. 14: Support the timing chain-Z20, Z22, Z24 and Z24i engines



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Fig. Fig. 15: Camshaft knockpin positioning-Z24i engines



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Fig. Fig. 16: Camshaft sprocket alignment-Z24i engines



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Fig. Fig. 17: Cylinder head bolt loosening sequence-Z20, Z22, Z24 and Z24i engines (L-series engines similar)

VG30i Engines

See Figures 18, 19, 20, 21, 22, 23, 24 and 25

To remove or install the cylinder head, you'll need a special hex head wrench ST10120000 (J24239-01) or equivalent. The collector assembly and intake manifold have special bolt sequence for removal and installation. The distributor assembly is located in the left cylinder head; mark and remove it if necessary.

  1. Release the fuel pressure. See the procedure in this section for timing belt removal. Set the engine to TDC and then remove the timing belt.
  2.  

Do not rotate either the crankshaft or camshaft from this point onward, or the valves could be bent by hitting the pistons.

  1. Drain the coolant from the engine. Tag and disconnect all the vacuum hoses and water hoses connected to the intake collector.
  2.  
  3. Remove the collector cover and the collector. Refer to the section Intake Manifold Removal And Installation for correct bolt removal sequence.
  4.  
  5. Remove the intake manifold and fuel tube assembly.
  6.  
  7. Remove the exhaust collector bracket. Remove the exhaust manifold covers. Disconnect the exhaust manifold when it connects to the exhaust pipe (three bolts).
  8.  
  9. Remove the camshaft pulleys and the rear timing cover securing bolts.
  10.  
  11. Loosen the cylinder head bolts a little at a time, in the order shown.
  12.  
  13. Remove the cylinder head with the exhaust manifold attached. If you need to remove the exhaust manifold, refer to the procedure in this section.
  14.  

To install:
  1. Check the positions of the timing marks and camshaft sprockets to make sure they have not shifted. The mark on the crankshaft should be aligned with the one on the oil pump body and the camshaft knockpin should be at the top.
  2.  
  3. Install the head with a new gasket. Apply clean engine oil to the threads and seats of the bolts, then install the bolts with washers (beveled edges up) in the correct position. Note that bolts 4, 5, 12 and 13 are longer than the others.
  4.  
  5. Tighten the bolts in the proper sequence, in the following stages:
    1. Tighten all bolts, in order, to 22 ft. lbs. (29 Nm)
    2.  
    3. Tighten all bolts, in order, to 43 ft. lbs. (59 Nm)
    4.  
    5. Loosen all bolts completely.
    6.  
    7. Tighten all bolts, in order, to 22 ft. lbs. (29 Nm)
    8.  
    9. Tighten all bolts, in order, to 40-47 ft. lbs. (54-64 Nm). Or, if you have an angle torque wrench available, tighten them 60-65 degrees tighter rather than to the final torque.
    10.  

  6.  
  7. Install the rear timing cover bolts. Install the camshaft pulleys. Make sure the pulley marked R3 goes on the right and that marked L3 goes on the left.
  8.  
  9. Align the timing marks if necessary and then install the timing belt and adjust the belt tension.
  10.  
  11. Install the front upper and lower belt covers.
  12.  
  13. Make sure that the cylinder head cover bolts, trays and washers are free of oil. Then, install the cylinder head covers.
  14.  
  15. Install the intake manifold and fuel tube.
  16.  
  17. Install the exhaust manifold if removed from the cylinder head.
  18.  
  19. Connect the exhaust manifold to the exhaust pipe connection. Install the exhaust collector bracket.
  20.  
  21. Install the collector and collector cover. Refer to the section for Intake Manifold Removal And Installation for the correct torque pattern.
  22.  
  23. Connect all the vacuum hoses and water hoses to the intake collector.
  24.  
  25. Refill the cooling system. Start the engine and then check the engine timing. After the engine reaches the normal operating temperature, check for the correct coolant level.
  26.  
  27. Roadtest the vehicle for proper operation.
  28.  



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Fig. Fig. 18: Exploded view of the cylinder head-VG30i engines



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Fig. Fig. 19: Cylinder head bolt loosening sequence-1986-87 VG30i engines



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Fig. Fig. 20: Cylinder head bolt loosening sequence-1988 VG30i engines



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Fig. Fig. 21: Crankshaft sprocket alignment-VG30i engines



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Fig. Fig. 22: Cylinder head bolt tightening sequence-VG30i engines



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Fig. Fig. 23: Install the cylinder head bolt washer this way-VG30i engines



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Fig. Fig. 24: Camshaft sprocket installation and positioning-VG30i engines



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Fig. Fig. 25: Camshaft sprocket timing marks-VG30i engines

SD22 and SD25 Engines

See Figures 26, 27 and 28

  1. Remove the air cleaner.
  2.  
  3. Remove the crankcase vent hose, then remove the intake and exhaust manifolds. These are bolted together.
  4.  
  5. Remove the alternator, bracket and belts.
  6.  
  7. Disconnect the coolant hose between the head and the oil cooler.
  8.  
  9. Remove the fuel filter assembly.
  10.  
  11. Disconnect the injection lines from the pump and the injectors. Cap all openings at once.
  12.  
  13. Remove the bypass hoses between the coolant pump and the thermostat housing.
  14.  
  15. Remove the fan.
  16.  
  17. Remove the rocker arm cover.
  18.  
  19. Remove the rocker arm shaft assembly.
  20.  
  21. Remove the pushrods and keep them in order.
  22.  
  23. Remove the fuel return lines.
  24.  
  25. Remove the injection nozzles from the cylinder head.
  26.  
  27. Remove the cylinder head bolts gradually, in the sequence shown.
  28.  
  29. Attach a hoist to the head and lift it clear of the block. On occasion, the precombustion chambers may fall out, especially if the head is bumped or handled roughly. Take care that they are returned to their original positions if this occurs.
  30.  

To Install:
  1. Remove the head gasket and O-rings.
  2.  
  3. Clean and inspect all parts.
  4.  
  5. Check the head with a straightedge. Maximum warpage is 0.0079 in. (0.2mm). Do not remove more than 0.011 in. (0.28mm) from the head.
  6.  
  7. Place a new cylinder head gasket on the block with the stainless steel inset side facing up.
  8.  
  9. Install the O-rings around the water and oil passages.
  10.  
  11. Position the cylinder head on the engine block.
  12.  
  13. Coat the head bolts with clean engine oil and tighten them using stages of the proper sequence:
    1. Tighten the main (large) bolts to 43-58 ft. lbs. (59-78 Nm)
    2.  
    3. Tighten the sub (small) bolts to 14-22 ft. lbs. (20-29 Nm)
    4.  
    5. Tighten the main bolts to 87-94 ft. lbs. (118-127 Nm)
    6.  
    7. Tighten the sub bolts to 33-40 ft. lbs. (44-54 Nm)
    8.  

  14.  
  15. Install the pushrods, pressing down and turning them to be sure of proper seating.
  16.  
  17. Install the rocker arm shaft assembly, tighten the bolts to 18 ft. lbs. (24 Nm) in sequence from the center to each end.
  18.  
  19. Install the injection nozzles.
  20.  
  21. Install the remaining components as they were removed.
  22.  



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Fig. Fig. 26: Exploded view of the cylinder head-SD25 engines (SD22 engines similar)



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Fig. Fig. 27: Cylinder head bolt loosening sequence-SD22 and SD25 engines



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Fig. Fig. 28: Cylinder head bolt tightening sequence-SD22 and SD25 engines

CLEANING AND INSPECTION



See Figures 33, 34 and 35

When the rocker assembly and valve train have been removed from the cylinder head (see Valves and Springs below), set the cylinder head on two wooden blocks on the bench, combustion chamber side up. Using a scraper or putty knife, carefully scrape away any gasket material that may have stuck to the head-to-block mating surface when the head was removed. Make sure you DO NOT gouge the mating surface with the tool.

Using a wire brush chucked into your electric drill, remove the carbon in each combustion chamber. Make sure the brush is actually removing the carbon and not merely burnishing it.

Clean all the valve guides using a valve guide brush (available at most auto parts or auto tool shops) and solvent. A fine-bristled rifle bore cleaning brush also works here.

Inspect the threads of each spark plug hole by screwing a plug into each, making sure it screws down completely. Heli-coil® any plug hole this is damaged.


CAUTION
DO NOT hot tank the cylinder head! The head material on most engines is aluminum, which is ruined if subjected to the hot tank solution. Some of the early engines were equipped with cast iron heads, which can be hot-tanked (a service performed by most machine shops which immerses the head in a hot, caustic solution for cleaning). To be sure your engine's cylinder head is aluminum, check around its perimeter with a magnet. Your engine has an iron head if the magnet sticks.

Before hot-tanking any overhead cam cylinder head, check with the machine shop doing the work. Some cam bearings are easily damaged by the hot tank solution.

Finally, go over the entire head with a clean shop rag soaked in solvent to remove any grit, old gasket particles, etc. Blow out the bolt holes, coolant galleys, intake and exhaust ports, valve guides and plug holes with compressed air.



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Fig. Fig. 33: Remove the carbon from the cylinder head with a wire brush and electric drill



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Fig. Fig. 34: Do not scratch the cylinder head mating surface when removing the old gasket material



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Fig. Fig. 35: Check the cylinder head mating surface straightness with a precision straightedge and a feeler gauge

RESURFACING



See Figures 36 and 37

While the head is removed, check the head-to-block mating surface for straightness. If the engine has overheated and blown a head gasket, this must be done as a matter of course. A warped mating surface must be resurfaced (milled); this is done on a milling machine and is quite similar to planing a piece of wood.

Using a precision steel straightedge and a blade-type feeler gauge, check the surface of the head across its length, width and diagonal length as shown in the illustrations. Also check the intake and exhaust manifold mating surfaces and cam cover (all) mating surfaces. If warpage exceeds 0.003 in. (0.08mm) in a 6 in. (152mm) span, or 0.005 in. (0.15mm) over the total length, the head must be milled. If warpage is highly excessive, the head must be replaced. Again, consult the machine shop operator on head milling limitations.



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Fig. Fig. 36: Check the engine block mating surface straightness with a precision straightedge and a feeler gauge



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Fig. Fig. 37: Removing carbon from the piston tops-do not scratch the pistons

CYLINDER BLOCK CLEANING



While the cylinder head is removed, the top of the cylinder block and pistons should also be cleaned. Before you begin, rotate the crankshaft until one or more pistons are flush with the top of the block (on the four cylinder engines, you will either have Nos. 1 and 4 up, or Nos. 2 and 3 up). Carefully stuff clean rags into the cylinders in which the pistons are down. This will help keep grit and carbon chips out during cleaning. Using care not to gouge or scratch the block-to-head mating surface and the piston top(s), clean away any old gasket material with a wire brush and/or scraper. On the piston tops, make sure you are actually removing the carbon and not merely burnishing it.

Remove the rags from the down cylinders after you have wiped the top of the block with a solvent soaked rag. Rotate the crankshaft until the other pistons come up flush with the top of the block, and clean those pistons.

Because you have rotated the crankshaft, you will have to re-time the engine following the procedure listed under the Timing Chain/Timing Belt removal. Make sure you wipe out each cylinder thoroughly with a solvent-soaked rag, to remove all traces of grit, before the head is reassembled to the block.

 
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