REMOVAL & INSTALLATION
Although, in most cases, the pistons and connecting rods can be removed from the engine (after the cylinder head and oil pan are removed) while the engine is still in the car, it is far easier to remove the engine from the car.
- Remove the cylinder head as outlined in the appropriate preceding section.
- Remove the oil pan and pump.
- Because the top piston ring does not travel to the very top of the cylinder bore, a ridge is built up between the end of the travel and the top of the cylinder. Pushing the piston and connecting rod assembly past the ridge is difficult and may cause damage to the piston. If new rings are installed and the ridge has not been removed, ring breakage and piston damage can occur when the ridge is encountered at engine speed.
- Turn the crankshaft to position the piston at the bottom of the cylinder bore. Cover the top of the piston with a rag. Install a ridge reamer in the bore and follow the manufacturer's instructions to remove the ridge. Use caution. Avoid cutting too deeply or into the ring travel area. Remove the rag and cuttings from the top of the piston. Remove the ridge from all cylinders.
- Check the edges of the connecting rod and bearing cap for numbers or matchmarks, if none are present mark the rod and cap numerically and in sequence from front to back of engine. The numbers or marks not only tell from which cylinder the piston came from but also ensures that the rod caps are installed in the correct matching position.
- Turn the engine until the connecting rod to be serviced is at the bottom of travel. Unbolt the connecting rod caps. Mark the caps with the number of the cylinder from which they were removed. Place two pieces of rubber hose over the rod cap bolts and push the piston and rod assembly up through the top of the cylinder bore.
- Mark the pistons and connecting rods with the numbers of the cylinders from which they were removed.
- Apply a light coating of engine oil to the pistons, rings, and wrist pins.
- Examine the piston to ensure that it has been assembled with its parts positioned correctly. (See the illustrations.) Be sure that the ring gaps are not pointed toward the thrust face of the piston and that they do not overlap.
- Install the pistons, using a ring compressor, into the cylinder bore. Be sure that the appropriate marks on the piston are facing the front of the cylinder.
It is important that the pistons, rods, bearings, etc., be returned to the same cylinder bore from which they were removed.
- Clean the rod journal, the connecting rod end and the bearing cap after removing the old bearing inserts. Install the new inserts in the rod and bearing cap, lubricate them with oil. Position the rod over the crankshaft journal and install the rod cap. Make sure the cap and rod numbers match, tighten the rod nuts to specifications.
Be sure that the mating marks on the connecting rods and rod bearing caps are aligned.
- The rest of the removal procedure is performed in the reverse order of installation.
CLEANING AND INSPECTION
- Use a piston ring expander and remove the rings from the piston.
- Clean the ring grooves using an appropriate cleaning tool, exercise care to avoid cutting too deeply.
- Clean all varnish and carbon from the piston with a safe solvent. Do not use a wire brush or caustic solution on the pistons.
- Inspect the pistons for scuffing, scoring, cracks, pitting or excessive ring groove wear. If wear is evident, the piston must be replaced.
- 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.
Check the cylinder bore for wear 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 0.010 in. (0.25mm) or larger oversized pistons installed.
FITTING AND POSITIONING PISTON RINGS
- 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.
- 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.
- 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.
- Check the ring grooves 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.
Always add spacers above the piston ring.
- Install the ring on the piston, lower oil ring first. Use a ring installing tool on the compression rings. 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.
- When installing oil rings, first, install the expanding 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.
- Install the two compression rings.
- Install the rings in their proper order, install a ring compressor and insert the piston and rod assembly into the engine.
PISTON PIN REPLACEMENT
- Using a suitable pair of snapring pliers or equivalent, remove the snaprings from the side of the piston.
- Gradually heat the pistons to approximately 140°F (60°C).
- Place the piston upside down in a suitable holding fixture and using a plastic mallet and a brass drift, drive out the piston pin and remove the connecting rod.
- Be sure to arrange the piston pins, rings, connecting rods and bearings in the correct order. The pistons and pins are a matched set.
- Check the connecting rod bushing and the piston pin for damage and wear and replace as necessary.
- To replace the connecting rod bushing, use a suitable hydraulic press, place the connecting rod in a holding fixture and press out the old bushing.
- Align the oil holes of a new bushing with those of the connecting rod. Using the same press, press in the new bushing.
- Check the fit of the piston pin in the connecting rod bushing. Coat the pin with engine oil and push it into the connecting rod bushing with your thumb. If the pin is to tight it will be necessary to hone the new bushing.
- Gradually heat the pistons to approximately 140°F (60°C). Install a snapring to one side of the piston. Install the connecting rod into the piston and push in a new piston pin with your thumb. If the pin can be installed at a lower temperature, replace the piston.
- Install a snapring to the other side of the piston.