- Remove the cylinder head.
- Remove the oil pan.
- Remove any carbon buildup from the cylinder wall at the top end of the piston travel with a ridge reamer tool.
- Position the piston to be removed at the bottom of its stroke so that the connecting rod bearing cap can be reached easily from under the engine.
- Unscrew the connecting rod bearing cap nuts and remove the cap and lower half of the bearing. Cover the rod bolts with lengths of rubber tubing or hose to protect the cylinder walls when the rod and piston assembly is driven out.
- Push the piston and connecting rod up and out of the cylinder block with a length of wood. Use care not to scratch the cylinder wall with the connecting rod or the wooden tool.
Except LD28 Diesel/Engine
- Keep all of the components from each cylinder together and install them in the cylinder from which they were removed.
- Coat the bearing face of the connecting rod and the outer face of the pistons with engine oil.
- See the illustrations, the correct placement of the piston rings for your model and engine size.
- Turn the crankshaft until the rod journal of the particular cylinder you are working on is brought to the TDC position.
- With the piston and rings clamped in a ring compressor, the notched mark on the head of the piston toward the front of the engine, and the oil hole side of the connecting rod toward the fuel pump side of the engine, push the piston and connecting rod assembly into the cylinder bore until the big bearing end of the connecting rod contacts and is seated on the rod journal of the crankshaft. Use care not to scratch the cylinder wall with the connecting rod.
See LD28 Diesel below for piston installation details on that engine.
- Push down farther on the piston and turn the crankshaft while the connecting rod rides around on the crankshaft rod journal. Turn the crankshaft until the crankshaft rod journal is at BDC (bottom dead center).
- Align the mark on the connecting rod bearing cap with that on the connecting rod and tighten the bearing cap bolts to the specified torque.
- Install all of the piston/connecting rod assemblies in the manner outlined above.
- Install the oil strainer, pickup tube and oil pan.
- Install the cylinder head.
- Install engine assembly in vehicle.
- Check all fluid levels and road test.
When replacing pistons in the LD28 diesel engine, the amount of projection of each piston crown above the deck of the block must be measured.
- Clean the deck of the cylinder block completely.
- Set a dial gauge, as shown on the cylinder block surface in the illustration, to zero.
- For every cylinder, measure the piston projection and record the length.
Be sure to measure the length of piston projection at at least three points for every cylinder.
- Determine the maximum length of piston projection and select the suitable head gasket according to the chart below.
The head gaskets have cutout(s) in them for identification purposes. When a head gasket needs to be replaced, always install a gasket of the same thickness.
CLEANING & INSPECTION
Clean the piston after removing the rings (See Piston Ring and Wrist Pin Removal and Installation), 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. (See Piston Ring Side Clearance Check for more details). 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 may have to have the pistons measured 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 an oiled cylinder, and sliding in a feeler gauge between the two.
When any one cylinder needs boring, all cylinders must be bored.
IDENTIFICATION & POSITIONING
The pistons are marked with a number or F in the piston head. When installed in the engine the number or F markings are to be facing toward the front of the engine.
The connecting rods are installed in the engine with the oil hole facing toward the fuel pump side (right) of the engine.
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 in the same direction from which they are removed.
PISTON RING & WRIST PIN REMOVAL
A piston ring expander is necessary for removing piston rings without damaging them; any other method (prytool blades, pliers, etc.) usually results in the rings being bent, scratched or distorted, or the piston itself being damaged. When the rings are removed, clean the ring grooves using an appropriate ring groove cleaning tool, using care not to cut too deeply. Thoroughly clean all carbon and varnish from the piston with solvent.
All the Datsun/Nissan pistons covered in this guide have a pressed in wrist pin, requiring a special press for removal. Take the piston and connecting rod assemblies to an engine specialist or machinist for wrist pin removal. The pins must also be pressed in during assembly.
PISTON RING END-GAP
Piston ring end-gap should be checked while the rings are removed from the pistons. Incorrect end-gap indicates that the wrong size rings are being used; ring breakage could occur.
Compress the piston rings to be used in a cylinder, one at a time, into that cylinder. Squirt clean oil into the cylinder, so that the rings and the top 50mm of cylinder wall are coated. Using an inverted piston, press the rings approximately 25mm below the deck of the block. Measure the ring end-gap with a feeler gauge, and compare to the Ring Gap chart in this section. Replace the ring if necessary.
PISTON RING SIDE CLEARANCE CHECK & INSTALLATION
Check the pistons to see that the ring grooves and oil return holes have been properly cleaned. Slide a piston ring into its groove, and check the side clearance with a feeler gauge. On gasoline engines, make sure you insert the gauge between the ring and its lower land (lower edge of the groove), because any wear that occurs forms a step at the inner portion of the lower land. If the piston grooves have worn to the extent that relatively high steps exist on the lower land, the piston should be replaced, because these will interfere with the operation of the new rings and ring clearances will be excessive. Piston rings are not furnished in oversize widths to compensate for ring groove wear.
Install the rings on the piston, lowest ring first, using a piston ring expander. There is a high risk of breaking or distorting the rings, or scratching the piston, if the rings are installed by hand or other means.
Position the rings on the piston as illustrated; spacing of the various piston ring gaps is crucial to proper oil retention and even cylinder wear. When installing new rings, refer to the installation diagram furnished with the new parts.
CONNECTION ROD INSPECTION & BEARING REPLACEMENT
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® gauging material you will be using to check clearances with 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 car and inverted). Reinstall the cap and torque to specifications listed in the Torque Specifications chart.
- Remove the rod cap and determine 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 from 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 with the naked eye.