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 work on the engine when removed from the car.
If removing pistons with the engine still installed, disconnect the radiator hoses, automatic transmission cooler lines and radiator shroud. Unbolt the front mounts before raising the engine. Block the engine in position with wooden blocks between the mounts.
- Remove the engine from the car. Remove the cylinder head(s), oil pan and front cover (if necessary).
- 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 ring 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. 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 the engine. The numbers or marks not only tell which cylinder the piston came from, but also helps ensure that the rod caps are installed in the correct matching position.
- Turn the crankshaft until the connecting rod is at the bottom of travel. Remove the two attaching nuts and the bearing cap. Take two pieces of rubber tubing and cover the rod bolts to prevent crank or cylinder scoring. Use a wooden hammer handle to help push the piston and rod up and out of the cylinder. Reinstall the rod cap in its proper position. Remove all pistons and connecting rods. Inspect cylinder walls and deglaze or hone them as necessary.
- Installation is in the reverse order of removal. Lubricate each piston, rod bearing and cylinder wall. Install a ring compressor over the piston, position the piston with the mark toward the front of the engine and carefully install it into the engine. Position the connecting rod with the bearing insert installed over the crankshaft journal. Install the rod cap with the bearing in the proper position. Secure it with rod nuts and tighten them to the proper specifications. Install all rod and piston assemblies.
CLEANING & 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 a qualified automotive machine shop.
- Check the cylinder bore for wear using a telescoping gauge and a micrometer, measure the cylinder bore diameter perpendicular to the piston pin at a point 2 1 / 2 inches 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 .010 inch or larger oversized pistons installed.
FITTING & 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 inch 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, which is referred to as ring end-gap. Compare the reading to the one called for in the specifications chart. File the ends of the ring with a fine file to obtain necessary clearance.
If inadequate ring end-gap is utilized, ring breakage will result.
- 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 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.
When necessary, always add spacers above the piston ring.
- 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.
- 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 inch away from the butted end of the control ring. Install the top rail about 1 inch away from the butted end of the control but on the opposite side from the lower rail.
- Install the two compression rings.
- Consult the illustration for ring positioning, arrange the rings as shown, install a ring compressor and insert the piston and rod assembly into the engine.