Piston: Service and Repair
1. Remove any carbon or ridge at the top of the cylinder bore with a ridge remover to avoid damage to piston ring ends.
2. Mark connecting rod caps to indicate cylinder number and orientation of cap.
3. Remove connecting rod cap bolts and remove caps. Push connecting rods away from crankshaft.
4. Remove each piston and rod assembly from block and reinstall the appropriate rod cap to the assembly.
NOTICE: Do not mix the rod caps with other rods.
5. Remove the piston rings by expanding them and sliding them off pistons.
CAUTION: Take care when removing piston rings as worn rings may have sharp edges.
6. Place the piston and connecting rod assembly into fixture J 24086 and press out the piston pin. This applies to non-supercharged engines only. See Steps 7 and 8 for supercharged engine piston pin removal.
NOTICE: The piston pins used in supercharged engines are retained by two (2) retainers. No special tools are required to remove or install the retainers or piston pin. The retainer may be reused if they are not damaged.
7. Remove two piston pin retainers.
8. Remove piston pin.
9. Check cylinder bore, with bore gage, measure for wear, taper, out-of-round and ridging.
NOTICE: If the bore is worn beyond limits, it may be re-bored, honed, and fitted with oversize pistons. The smallest available oversize should be selected.
NOTICE: When reboring cylinder bores, all crankshaft bearing caps must be in place and tightened to specified torque to prevent distortion of bores.
10. When new piston rings are installed without reboring cylinders, the glazed cylinder walls should be slightly dulled, but without increasing the bore diameter, using the finest grade of stone in a cylinder hone.
11. Clean carbon from piston heads. Clean carbon from ring grooves with suitable tool and remove any gum or varnish from piston skirts with suitable cleaning solvents.
12. Carefully examine piston skirt for rough or scored surfaces, cracks in skirt or crown, broken ring lands. Chipping or uneven wear which would cause rings to seat improperly or have excessive clearance in ring grooves. Damaged or faulty pistons should be replaced.
13. Inspect piston pin bores and piston pins for wear. Piston pin bores and piston pins must be free of varnish or scuffing when being measured. The piston should be measured with a micrometer and piston pin bore should be measured with a dial bore gage or an inside micrometer. If clearance is not to specification piston pin should be replaced.
14. To check piston to bore clearance subtract piston diameter from cylinder bore diameter.
NOTICE: Scrub the cylinder bore and piston with soap and water and remove all foreign material. Dry and rub in clean engine oil.
15. Remove bearing shells from connecting rod, install cap and bolts. Tighten bolts to the correct torque specification.
16. Place connecting rod assembly on a checking fixture and check rod for bend or twist. If the connecting rod is bent more than .127 mm (.005 inch) measured over the entire length of the connecting rod, .it must be replaced. If the connecting rod is twisted more than .254mm (0.010 inch) measured oyer the entire length of the connecting rod, it must be replaced.
NOTICE: Do not attempt to straighten any connecting rod. Always check new connecting rods before using them.
17. Inspect outside of connecting rod bearing shells and internal diameter of connecting rod big end for wear indicating high spots in rod big end. Inspect connecting rod bolts for stretching by comparing them with a new bolt.