Dodge Omni/Horizon/Rampage 1978-1989 Repair Guide

Pistons and Connecting Rods

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REMOVAL & INSTALLATION





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Fig. Fig. 1 Piston and connecting rod on the 1.6L engine



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Fig. Fig. 2 Piston and connecting rod on the 1.7L engine



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Fig. Fig. 3 Piston and connecting rod used on 2.2L engines


WARNING
This procedure is much easier performed with the engine out of the car.

  1. Remove the cylinder head.
  2.  
  3. Remove the oil pan.
  4.  
  5. Pistons should be removed in the order: 1-3-4-2. Turn the crankshaft until the piston to be removed is at the bottom of its stroke.
  6.  
  7. Place a cloth on the head of the piston to be removed and, using a ridge reamer, remove the deposits from the upper end of the cylinder bore.
  8.  


WARNING
Never remove more than 0.03 in. (0.8mm) from the ring travel area when removing the ridges.

  1. Mark all connecting rod bearing caps so that they may be returned to their original locations in the engine. The connecting rod caps are marked with rectangular forge marks which must be mated during assembly and be installed on the intermediate shaft side of the engine. Mark all pistons so they can be returned to their original cylinders.
  2.  
  3. Remove the bearing caps, then place a length of hose over the studs.
  4.  
  5. Carefully tap the piston and rod assembly out of the bore.
  6.  


WARNING
Don't score the cylinder walls or the crankshaft journal.

To install:

  1. Carefully tap the piston out of the bore using a wooden dowel
  2.  
  3. Install the pistons in their original bores, if you are reusing the same pistons. Install short lengths of rubber hose over the connecting rod bolts to prevent damage to the cylinder walls or rod journal.
  4.  
  5. Installing the piston into the block using a ring compressor and the handle of a hammer
  6.  

  1. Install a ring compressor over the rings on the piston. Lower the piston and rod assembly into the bore until the ring compressor contacts the block. Using a wooden hammer handle, push the piston into the bore while guiding the rod onto the journal.
  2.  


WARNING
On the 1.7 and 2.2L engines the arrow on the piston should face toward the front (drive belt) of the engine.

CLEANING AND INSPECTION



  1. Use a piston ring expander and remove the rings from the piston.
  2.  



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Fig. Fig. 7 Use a ring expander tool to remove the piston rings



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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 ring grooves, BUT be careful the ring is sharp

  1. Clean the ring grooves using an appropriate cleaning tool, exercise care to avoid cutting too deeply.
  2.  
  3. Clean all varnish and carbon from the piston with a safe solvent. Do not use a wire brush or caustic solution on the pistons.
  4.  
  5. Inspect the pistons for scuffing, scoring, cracks, pitting or excessive ring groove wear. If wear is evident, the piston must be replaced.
  6.  
  7. Have the piston and connecting rod assembly checked by a machine shop for correct alignment, piston pin wear and piston diameter. If the piston has collapsed it will have to be replaced or knurled to restore original diameter. Connecting rod bushing replacement, piston pin fitting and piston changing can be handled by the machine shop.
  8.  

CYLINDER BORE



Check the cylinder bore for wearing using a telescope gauge and a micrometer, measure the cylinder bore diameter perpendicular to the piston pin at a point 2 1 / 2 in. (63.5mm) below the top of the engine block. Measure the piston skirt perpendicular to the piston pin. The difference between the two measurements is the piston clearance. If the clearance is within specifications, finish honing or glaze breaking is all that is required. If clearance is excessive a slightly oversize piston may be required. If greatly oversize, the engine will have to be bored and 0.01 in. (0.25mm) or larger oversized pistons installed.



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Fig. Fig. 10 Measure the piston's outer diameter using a micrometer



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Fig. Fig. 11 A telescoping gauge may be used to measure the cylinder bore diameter

PISTON PINS



The pin connecting the piston and connecting rod is press fitted. If too much free-play develops take the piston assemblies to the machine shop and have oversize pins installed. Installing new rods or pistons requires the use of a press; have the machine shop handle the job for you.

FITTING PISTON RINGS



  1. Take the new piston rings and compress them, one at a time into the cylinder that they will be used in. Press the ring about 1 in. (25mm) below the top of the cylinder block using an inverted piston.
  2.  
  3. Use a feeler gauge and measure the distance between the ends of the ring, this is called, measuring the ring end-gap. Compare the reading to the one called for in the specifications table. File the ends of the ring with a fine file to obtain necessary clearance.
  4.  


WARNING
If inadequate ring end-gap is utilized ring breakage will result.

  1. Inspect the ring grooves on the piston for excessive wear or taper. If necessary have the grooves recut for use with a standard ring and spacer. The machine shop can handle the job for you.
  2.  
  3. Check the ring groove by rolling the new piston ring around the groove to check for burrs or carbon deposits. If any are found, remove with a fine file. Hold the ring in the groove and measure side clearance with a feeler gauge. If clearance is excessive, spacer(s) will have to be added.
  4.  



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Fig. Fig. 12 Piston rings must be installed in a specific order


WARNING
Always add spacers above the piston ring.

  1. Install the rings on the piston, lower ring first using a ring installing tool. Consult the instruction sheet that comes with the rings to be sure they are installed with the correct side up. A mark on the ring usually faces upward.
  2.  
  3. When installing oil rings, first install the ring in the groove. Hold the ends of the ring butted together (they must not overlap) and install the bottom rail (scraper) with the end about 1 in. (25mm) away from the butted end of the control ring. Install the top rail about 1 in. (25mm) away from the butted end of the control but on the opposite side from the lower rail.
  4.  
  5. Install the two compression rings.
  6.  
  7. Consult the illustration with piston ring set instruction sheet for ring positioning, arrange the rings, then install a ring compressor and insert the piston and rod assembly into the engine.
  8.  

 
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