Piston Grading Procedure
- If a new cylinder block and/or crankshaft is used, the piston grading procedure MUST be performed to determine the proper piston grade for each cylinder.- When rebuilding an engine with the original cylinder block, crankshaft and pistons, make sure the pistons are installed in their original cylinder.
- If replacing the piston(s), make sure the replacement piston(s) are the same grade as the one being replaced.
1. Install any of the original connecting rod and piston assemblies into the No. 1 cylinder. DO NOT install the piston rings.
2. Install the upper bearing shell in the connecting rod with the tang of the bearing in the slot of the connecting rod. The connecting rod bearing shell must be installed in the original connecting rod and cap. Use clean lubricating oil to coat the inside diameter of the connecting rod bearing shell.
3. Install the bearing shell in the connecting rod cap with the tang of the bearing in the slot to the cap. Use clean lubricating oil to coat the inside diameter of the bearing shell.
4. The number stamped on the connecting rod and cap at the parting line must match and be installed on the oil cooler side of the engine. Install the connecting rod cap and capscrews. Tighten the capscrews to 35 Nm (26 ft. lbs.) torque.
5. Use a fine grit stone to remove any burrs from the cylinder block head deck. Zero the dial indicator to the cylinder block head deck.
6. Move the dial indicator directly over the piston pin to eliminate any side-to-side movement.
7. Rotate the crankshaft to top dead center (TDC). Rotate the crankshaft clockwise and counterclockwise to find the highest dial indicator reading. Record the reading.
8. Remove the piston and connecting rod assembly from the No.1 cylinder and install the assembly into the No.2 cylinder. Repeat the procedure for every cylinder using the same piston and connecting rod assembly.
Fig. 150
Piston Protrusion Chart
Fig. 151
9. Determine the grade of the piston being used by referring to the Piston Protrusion Chart. Four digits on top of the piston can be cross referenced by a letter to a Chrysler part number for replacement (Fig. 150). If the number on the piston cannot be seen, use the alternate method for determining grade by measuring from the top of the piston to the top of the piston pin bore to see what grade piston is used. Refer to the illustration and chart (Fig. 151).
Ideal piston protrusion is 0.610 to 0.711 mm (0.024 to 0.023 in.).
Alternative Grade Identification Method
Use the table when piston grading numbers are missing or not legible.
DISASSEMBLY
Fig. 152
1. Remove the retaining rings from the piston (Fig. 152).
2. Slide the piston pin out of the bore. Heating the connecting rod is not required.
Fig. 159
3. Remove the piston rings (Fig. 159).
CLEANING
Pistons
Clean the pistons and pins in a suitable solvent, rinse in hot water and blow dry with compressed air. Soaking the pistons over night will loosen most of the carbon build up. De-carbon the ring grooves with a broken piston ring and again clean the pistons in solvent.
Rinse in hot water and blow dry with compressed air.
Connecting Rods
Clean the connecting rods in a suitable solvent, rinse in hot water and blow dry with compressed air.
INSPECTION
Pistons
Fig. 153
Inspect the pistons for damage and excessive wear. Check top of the piston, ring grooves, skirt and pin bore. Measure the piston skirt diameter (Fig. 153). If the piston is out of limits, replace the piston.
Fig. 154
Uses new piston rings to measure the ring side clearance (Fig. 154). Refer to the illustration and chart for specifications.
Fig. 155
Measure the pin bore (Fig. 155). The maximum diameter is 40.025 mm (1.5758 inch). If the bore is over limits, replace the piston.
Fig. 156
Inspect the piston pin for nicks, gouges and excessive wear. Measure the pin diameter (Fig. 156). The minimum diameter is 39.990 mm (1.5744 inch). If the diameter is out of limits, replace the pin.
Connecting Rods
Inspect the connecting rod for damage and wear.
The I-Beam section of the connecting rod cannot have dents or other damage. Damage to this part can cause stress risers which will progress to breakage.
Fig. 157
Measure the connecting rod pin bore (Fig. 157). The maximum diameter is 40.042 mm (1.5764 inch). If out of limits, replace the connecting rod.
ASSEMBLY
NOTE: The piston is symmetrical and can be installed to the connecting rod in either direction. It is good practice to re-install the piston in the same orientation as it was removed.
Fig. 158
1. Position the rod into the piston, orienting the mark you made on removal and the numbers on the rod and cap the same way (Fig. 158). Install the retaining ring into the pin groove on the one side of the piston.
2. Lubricate the pin and bore with engine oil.
3. Install the piston pin in the opposite side of the installed retaining pin. Pistons and rods do not require heating to install the pin, however, the piston does need to be at room temperature or above.
4. Determine the piston diameter and obtain the appropriate ring set. The piston rings can be identified as shown in (Fig. 159).
Fig. 160
5. Position each ring in the cylinder and use a piston to square it with the bore at a depth of 89.0 mm (3.5 inch) - (Fig. 160).
Part 1 Of 2:
Part 2 Of 2:
Fig. 161
6. Use a feeler gauge to measure the piston ring gap (Fig. 161).
7. The top surface of all of the rings are identified with the word TOP or the supplier's MARK. Assemble the rings with the word TOP or the supplier's MARK up.
8. Position the oil ring expander in the oil control ring groove (bottom groove).
Fig. 162
9. Install the oil control ring with the end gap OPPOSITE the ends on the expander (Fig. 162).
10. Install the intermediate piston ring in the second groove (Fig. 160).
Fig. 163
11. Install the top piston ring in the top groove (Fig. 163).
Fig. 164
12. Position the rings as shown in (Fig. 164).
Fig. 165
13. Install the original bearings as removed or install new bearings. If new bearings are used, be sure to obtain the proper bearing clearance (Fig. 165).
14. DO NOT lubricate the side of the bearing that is against the connecting rod or cap. Apply a coat of Lubriplate 105, or equivalent to the new upper and lower connecting rod bearings.
INSTALLATION
1. Lubricate the cylinder bores with clean engine oil.
2. Generously lubricate the rings and piston skirts with clean engine oil.
Fig. 166
3. Compress the rings using a piston ring compressor tool (Fig. 166). If using a strap-type ring compressor, make sure the inside end of the strap does not hook on a ring gap and break the ring.
Fig. 167
4. Bar the crankshaft so the rod journal for the piston to be installed is at BDC (Bottom Dead Center) - (Fig. 167).
5. Be sure the mark you made on the piston and the numbers on the rod and cap are oriented as illustrated.
6. Position the piston and rod assembly into the cylinder bore with the mark you made on the piston towards the front of the cylinder block. In this position the numbers on the connecting rod should be facing the oil cooler side of the engine, and the rod bolt holes toward the camshaft. Use care when you install the piston and connecting rod so the cylinder bore is not damaged.
7. Push the piston into the bore until the top of the piston is approximately 50 mm (2 inch) below the top of the block. Carefully pull the connecting rod onto the crankshaft journal.
8. Use clean engine oil to lubricate the threads and under the heads of the connecting rod bolts.
Fig. 168
9. The number stamped on the rod cap at the parting line must match and be installed towards the oil cooler side of the engine (Fig. 168).
10. Install the rod cap and bolts to the connecting rod. Tighten the connecting rod and bolt evenly in 3 steps.
- Tighten the bolts to 35 Nm (26 ft. lbs.) torque.
- Tighten the bolts to 70 Nm (51 ft. lbs.) torque.
- Tighten the bolts to 100 Nm (73 ft. lbs.) torque.
11. The crankshaft must rotate freely. Check for freedom of rotation as the caps are installed. If the crankshaft does not rotate freely, check the installation of the rod bearing and the bearing size.
Part 1 Of 2:
Part 2 Of 2:
Fig. 169
12. Measure the side clearance between the connecting rod and the crankshaft (Fig. 169). DO NOT measure the clearance between the cap and crankshaft.
13. Install the suction tube and oil pan.
14. Install the cylinder head onto the engine.
15. Install a new filter and fill the crankcase with new engine oil.
16. Connect the battery negative cables and start engine.