Pontiac Fiero 1984-1988 Repair Guide

Pistons and Connecting Rod Assemblies

Print

REMOVAL





Click image to see an enlarged view

Fig. Fig. 1 Place rubber hose over the connecting rod studs to protect the crank and bores from damage



Click image to see an enlarged view

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

  1. Remove the engine assembly from the car, by following the Engine removal and installation procedures, earlier in this section.
  2.  
  3. On 6-cylinder engines, remove the intake manifold and the cylinder head over piston assembly being removed. On 4-cylinder engines, remove the cylinder head and manifolds as an assembly.
  4.  


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. Drain the oil and remove the oil pan.
  2.  
  3. Remove the oil pump assembly. On 1987-88 2.5L engines, remove the force balancer assembly as outlined in the Forced Balancer removal procedures.
  4.  
  5. Stamp the cylinder number on the machine surfaces of the bolt bosses of the connecting rod and cap for identification when reinstalling. If the pistons are to be removed from the connecting rod, mark the cylinder number on the piston with a silver pencil or quick drying paint for proper cylinder identification and cap-to-rod location. The 2.5L L4 engine (LR8) is numbered 1-4 from front to back; the 2.8L V6 engine (L44) is numbered 1-3-5 on the right bank, 2-4-6 on the left bank.
  6.  
  7. Examine the cylinder bore above the ring travel. If a ridge exists, remove the ridge with a ridge reamer before attempting to remove the piston and rod assembly.
  8.  
  9. Remove the rod bearing cap and bearing.
  10.  
  11. Install guide hoses over threads of the rod bolts. This is to prevent damage to bearing journal and rod bolt threads.
  12.  
  13. Remove the rod and piston assembly through the top of the cylinder bore by lightly tapping the connecting rod with a wooden hammer handle.
  14.  

If the piston rings will not clear the top of the cylinder, check to see if the ridge is completely removed.

  1. Remove all other rod and piston assemblies in the same manner.
  2.  

CLEANING & INSPECTION





Click image to see an enlarged view

Fig. Fig. 3 Clean the piston grooves using a ring groove cleaner



Click image to see an enlarged view

Fig. Fig. 4 You can use a piece of an old ring to clean the piston grooves, BUT be careful, the ring is sharp

Connecting Rods

Wash connecting rods in cleaning solvent and dry with compressed air. Check for twisted or bent rods and inspect for nicks or cracks. Also check the length of the rods and replace connecting rods that are damaged.

Pistons


Click image to see an enlarged view

Fig. Fig. 5 Use a micrometer to measure the piston skirt

Clean varnish from piston skirts and pins with a cleaning solvent. Do not wire brush any part of the piston. Clean the carbon out of the ring grooves with a ring groove cleaner or break a old ring in half. Make sure oil ring holes and slots are clean.

Inspect the piston for cracked ring lands, skirts or pin bosses, wavy or worn ring lands, scuffed or damaged skirts, eroded areas at the top of the piston. Replace pistons that are damaged or show signs of excessive wear. Inspect the grooves for nicks or burrs that might cause the rings to hang up.

Measure piston skirt (across center line of piston pin) and check piston clearance.

PISTON PIN REMOVAL & INSTALLATION





Click image to see an enlarged view

Fig. Fig. 6 Remove the piston pin using an arbor and a suitable piston pin tool



Click image to see an enlarged view

Fig. Fig. 7 Coat the piston pin with clean engine oil, then install it using an arbor press

Use care at all times when handling and servicing connecting rods and pistons. To prevent possible damage to these units, do not clamp the rod or piston in a vise since they may become distorted. Do not allow the pistons to strike against one another, against hard objects or bench surfaces, since distortion of the piston contour or nicks in the soft aluminum material may result.

  1. Remove the piston rings using a suitable piston ring remover.
  2.  
  3. Install the guide bushing of the piston pin removing and installing tool.
  4.  
  5. Install the piston and connecting rod assembly on a support, and place the assembly in an arbor press. Press the pin out of the connecting rod, using the appropriate piston pin tool.
  6.  
  7. When installing the new piston, apply clean engine oil to the pin and press in with a piston pin installing tool. Make sure the connecting rod moves freely without binding after pin is installed. If not, reaming the pin hole may have to be performed.
  8.  

MEASURING THE OLD PISTONS





Click image to see an enlarged view

Fig. Fig. 8 A telescoping gauge may be used to measure the cylinder bore diameter



Click image to see an enlarged view

Fig. Fig. 9 Measure the piston's outer diameter using 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 in the Piston and Connecting Rod chart in the beginning of this section. 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 0.25mm 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 cars, oversize pistons may be found. These pistons will be 0.25mm oversize. Aftermarket piston manufactures supply oversized pistons 0.030mm, 0.040mm, and 0.060mm in most cases.
  6.  
  7. After the cylinder has been reconditioned and new pistons purchased, remeasure bore and piston to ensure proper piston fit.
  8.  

CYLINDER HONING





Click image to see an enlarged view

Fig. Fig. 10 Typical cylinder bore wear patterns and measuring points



Click image to see an enlarged view

Fig. Fig. 11 Removing cylinder glazing using a flexible hone



Click image to see an enlarged view

Fig. Fig. 12 A solid hone can also be used to cross-hatch the cylinder bore



Click image to see an enlarged view

Fig. Fig. 13 As with a ball hone, work the hone carefully up and down the bore to achieve the desired results



Click image to see an enlarged view

Fig. Fig. 14 A properly cross-hatched cylinder bore

  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 imbedded 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.  

Handle pistons with care. Do not attempt to force pistons through cylinders until the cylinders have been honed to 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 with 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.  

CHECKING CYLINDER BORE





Click image to see an enlarged view

Fig. Fig. 15 Use a cylinder bore gauge to measure bore size and taper

Cylinder bore size can be measured with inside micrometers or a cylinder gauge. The most wear will occur at the top of the ring travel.

Reconditioned cylinder bores should be held to not more than 0.025mm taper.

If the cylinder bores are smooth, the cylinder walls should not be deglazed. If the cylinder walls are scored, the walls may have to be honed before installing new rings. It is important that reconditioned cylinder bores be thoroughly washed with a soap and water solution to remove all traces of abrasive material to eliminate premature wear.

 
label.common.footer.alt.autozoneLogo