REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12All Engines
Before removing the piston assemblies, connecting rod bearing clearance and side clearance should be checked. Refer to the Connecting Rod Inspection procedure in this section.
- Remove the cylinder head as outlined in the appropriate preceding section.
- Remove the oil pan and pump.
- Position a cylinder ridge reamer into the top of the cylinder bore. Keeping the tool square, ream the ridges from the top of the bore. Clean out the ridge material with a solvent-soaked rag, or blow it out with compressed air.
- Remove the oil strainer if it is in the way. Unbolt the connecting rod caps, after match marking each cap to its connecting rod.
- Place pieces of rubber hose over the rod bolts, to protect the cylinder walls and crank journals from scratches. Push the connecting rod and piston up and out of the cylinder from the bottom using a wooden hammer handle.
- Mark each connecting rod with the number of the cylinder from which it was removed. Number stamps are available at most hardware or auto supply stores.
- Apply a light coating of engine oil to the pistons, rings, and outer ends of the 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.
- Place pieces of rubber hose over the connecting rod bolts, to keep the threads from damaging the crank journal and cylinder bore. 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, bearing, etc., be returned to the same cylinder bore from which they were removed.
- Install the connecting rod bearing caps and tighten them to the torque figures given in the Torque Specifications chart.
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.
PISTON AND CONNECTING ROD IDENTIFICATION
See Figures 13, 14, 15, 16, 17, 18, 19, 20, 21 and 22
The pistons are marked with a notch in the piston head. When installed in the engine, the notch markings must be facing towards the front of the engine.
The connecting rods should be installed in the engine with the forged marks on the bearing caps and on the bottom of the rod facing toward the front of the engine also.
It is advisable to number the pistons, connecting rods and bearing caps in some manner so that they can be reinstalled in the same cylinder, facing the same direction, from which they were removed.
The piston rings must be installed with their gaps in the same position as shown in the illustrations below.
PISTON RING REPLACEMENT
See Figures 23, 24, 25, 26, 27 and 28
The cylinder walls must be de-glazed (honed) when the piston rings are replaced. De-glazing ensures proper ring seating and oil retention.
Using a piston ring expander, remove the rings one by one. Always remove and replace the rings of each piston before going on to the next. This helps avoid mixing up the rings. When the rings have been removed from each piston, perform the end gap and piston inspection and cleaning procedure below. The rings are marked on one side, the mark denoting the up side for installation.
Install the rings using the ring expander, starting with the top compression ring and working down. Make sure the marks are facing up on each ring. Position the rings so that the ring and gaps are set as in the illustrations. Never align the end gaps!
WRIST PIN REMOVAL & INSTALLATION
See Figures 29, 30, 32, 33, 34, 35, 36, 37 and 38
Wrist pin and/or connecting rod small-end bushing wear can be checked by rocking the piston at a right angle to the wrist pin by hand. If more than very slight movement is felt, the pin and/or rod busing must be replaced.
The pistons on the engines covered here must be heated in hot water to expand them before the wrist pins can be removed and installed. The four cylinder pistons must be heated to 176°F (80°C), and all six cylinder pistons must be heated to 140°F (60°C). This job can be performed at a machine shop if the idea of boiling pistons in the kitchen doesn't appeal to you. If you decide to do it, however, remember that each piston, pin and connecting rod assembly is a matched set and must be kept together until reassembly.
- Using needlenose or snapring pliers, remove the snaprings from the piston.
- Heat the piston(s) in hot water (as noted above depending on engine).
- Using a plastic-faced hammer and driver, lightly tap the wrist pin out of the piston. Remove the piston from the connecting rod.
- Assembly is in the opposite order of disassembly. The piston must again be heated to install the wrist pin and rod; it should be able to be pushed into place with your thumb when heated. When assembling, make sure the marks on the piston and connecting rod are aligned on the same side as shown.
CLEANING AND INSPECTION
Clean the piston after removing the rings, by first scraping any carbon from the piston top. Do not scratch the piston in any way during cleaning. Use a broken piston ring or ring cleaning tool to clean out the ring grooves. Clean the entire piston with solvent and a brush (NOT a wire brush).
Once the piston is thoroughly cleaned, insert the side of a good piston ring (both No. 1 and No. 2 compression on each piston) into its respective groove. Using a feeler gauge, measure the clearance between the ring and its groove. If clearance is greater than the maximum listed under Ring Side Clearance in the Piston and Ring chart, replace the ring(s) and if necessary, the piston.
To check ring end-gap, insert a compression ring into the cylinder. Lightly oil the cylinder bore and push the ring down into the cylinder with a piston, to the bottom of its travel. Measure the ring end-gap with a feeler gauge. If the gap is not within specification, replace the ring; DO NOT file the ring ends.
CYLINDER BORE INSPECTION
Place a rag over the crankshaft journals. Wipe out each cylinder with a clean, solvent-soaked rag. Visually inspect the cylinder bores for roughness, scoring or scuffing; also check the bores by feel. Measure the cylinder bore diameter with an inside micrometer, or a telescope gauge and micrometer. Measure the bore at points parallel and perpendicular to the engine centerline at the top (below the ridge) and bottom of the bore. Subtract the bottom measurements from the top to determine cylinder taper.
Measure the piston diameter with a micrometer; since this micrometer may not be part of your tool kit as it is necessarily large, you have to have the pistons miked at a machine shop. Take the measurements at right angles to the wrist pin center line, about an inch down the piston skirt from the top. Compare this measurement to the bore diameter of each cylinder. The difference is the piston clearance. If the clearance is greater than that specified in the Piston and Ring Specifications chart, have the cylinders honed or rebored and replace the pistons with an oversize set. Piston clearance can also be checked by inverting a piston into a oiled cylinder, and sliding in a feeler gauge between the two.
CONNECTING ROD INSPECTION AND BEARING REPLACEMENT
See Figures 39, 40 and 41
Connecting rod side clearance and big-end bearing inspection and replacement should be performed while the rods are still installed in the engine. Determine the clearance between the connecting rod sides and the crankshaft using a feeler gauge. If clearance is below the minimum tolerance, check with a machinist about machining the rod to provide adequate clearance. If clearance is excessive, substitute an unworn rod and recheck; if clearance is still outside specifications, the crankshaft must be welded and reground, or replaced.
To check connecting rod big-end bearing clearances, remove the rod bearing caps one at a time. Using a clean, dry shop rag, thoroughly clean all oil from the crank journal and bearing insert in the cap.
The Plastigage® gaging material you will be using to check clearances which is soluble in oil; therefore any oil on the journal or bearing could result in an incorrect reading.
Lay a strip of Plastigage® along the full length of the bearing insert (along the crank journal if the engine is out of the truck and inverted). Reinstall the cap and torque to specifications listed in the Torque Specifications chart.
Remove the rod cap and determine the bearing clearance by comparing the width of the now flattened Plastigage® to the scale on the Plastigage® envelope. Journal taper is determined by comparing the width of the Plastigage® strip near its ends. Rotate the crankshaft 90° and retest, to determine journal eccentricity.
Do not rotate the crankshaft with the Plastigage® installed.
If the bearing insert and crank journal appear intact and are within tolerances, no further service is required and the bearing caps can be reinstalled (remove Plastigage® before installation). If clearances are not within tolerances, the bearing inserts in both the connecting rod and rod cap must be replaced with undersize inserts, and/or the crankshaft must be reground. To install the bearing insert halves, press them into the bearing caps and connecting rods. Make sure the tab in each insert fits into the notch in each rod and cap. Lube the face of each insert with engine oil prior to installing each rod into the engine.
The connecting rods can be further inspected when they are removed form the engine and separated from their pistons. Rod alignment (straightness and squareness) must be checked by a machinist, as the rod must be set in a special fixture. Many machine shops also perform a Magnafluxing service, which is a process that shows up any tiny cracks that you may be unable to see.