Engine Inspection and Repair

CYLINDER HEAD INSPECTION

Visually inspect cylinder head for cracks or damage. Repair or replace as necessary.
Check for cylinder head distortion by placing a straightedge on the cylinder head mating surface. Measure the clearance between the straightedge and cylinder head surface with a feeler gauge Maximum permissible distortion is .004 inch across length and .010 inch across width. If distortion exceeds specifications, replace cylinder head.

VALVE SPRING INSPECTION

Examine valve springs for corrosion or damage. Replace if necessary. Measure free length of inner and outer springs. Minimum free length should be 1.654 inch for inner spring and 1.717 inch for outer spring. If measured length is less than specified, replace valve spring(s).

VALVE INSPECTION

Visually inspect valves for warping, cracks or excessive pitting. If damage is excessive, replace valve.
Measure valve stem diameter at several places with a micrometer. If valve stem diameter is less than .3102 inch for intake valve or .3097 inch for exhaust valve, replace valve(s).

CHECKING VALVE STEM TO GUIDE CLEARANCE

Position valve in guide, then mount a dial indicator so that pointer contacts valve stem. Move valve fore and aft and measure stem to guide clearance. Maximum allowable clearance for both intake and exhaust valves is .005 inch. If clearance is not within specifications, replace valve and guide.

PUSHROD INSPECTION

Visually inspect both ends of pushrod for wear or damage. If damage is excessive, replace pushrod. Measure pushrod deflection by positioning rod on a surface plate and measuring curvature with feeler gauge. Maximum allowable deflection is .0075 inch. If deflection is greater than specified limit, replace pushrod.

INSPECTING & REPAIRING PRE-CHAMBER INSERT

Visually inspect insert for cracks or breakage. If damage is evident, replace insert as follows:

Fig. 4 Removing pre-chamber insert:

1. Position metal rod into glow plug hole, then strike rod firmly with hammer until insert is pushed out of cylinder head, Fig. 4.
2. Install new insert, making sure projected portion of welch washer faces head gasket side of head. Stake welch washer by striking lightly with a suitable punch.

REPLACING VALVE GUIDE

1. Using service tool 49 0636 165A or equivalent, drive old guide out toward combustion chamber side of cylinder head.
2. Working from combustion chamber side of head, install and drive new guide into guide boss until guide protrudes exactly .650 inch above cylinder head.

REFACING VALVE

Reface the valves with a valve refacer, following the instructions of the valve refacer manufacturer. The intake valve face has a 45° angle, while the exhaust valve face has an angle of 30°. Take off only enough metal to assure a clean valve face. Make sure that the valve face contact area (valve margin) has a minimum width of .079 inch.

INSPECTING & REPAIRING VALVE SEAT

Visually inspect valve seat for cracks, burrs, ridges or improper angle or width. If it is necessary to cut the valve seat, use a valve seat cutter and cut intake valve seats to a 45° angle and exhaust valve seats to a 30° angle. Remove only enough metal to assure a smooth surface area.
After the valve seat is cut, check the contact area between the valve and seat as follows:
1. Apply a thin coat of Prussian Blue to valve seat, then press valve against seat.
2. Remove valve and observe the transfer of prussian blue to valve face. An even transfer indicates accurate valve and seat refacing. If transfer is uneven, hand lap the valve into the seat using suitable lapping compound.
3. Check valve seat width. Contact area should be located in center of valve face and seat, and seat width should be .079 inch for both intake and exhaust seats. If seat width is not as specified, service as required.

CHECKING VALVE STEM PROTRUSION

Fig. 5 Checking valve stem protrusion:

After valve and seat have been refaced, check the distance that valve stem protrudes above cylinder head, Fig. 5. Dimension ``L'' should be 1.890 inch. If dimension ``L'' is up to .020 inch greater than specified, no correction is necessary. If dimension ``L'' is .021-.059 inch greater than specified, install washers under lower spring seat to bring protrusion to stated value. If dimension ``L'' is .060 inch or greater than specified value, replace valve.

INSPECTION OF ROCKER ARM & SHAFT

The standard clearance between rocker arm bushing and shaft is .0028 inch. If clearance is greater than specified, replace rocker arm bushing or shaft.

CYLINDER BLOCK INSPECTION

Check cylinder block for cracks, cuts or damage and cooling and oil passages for blockage. Repair or replace as necessary. Check cylinder block for distortion. Maximum permissible distortion across width should be .0039 inch. Maximum permissible distortion across length should be .0098 inch. If distortion exceeds allowable limit, repair or replace cylinder block.

INSPECTING & REPLACING CYLINDER LINER

Fig. 6 Checking cylinder liner for wear:

Inspect the cylinder liner for wear and out of round at locations shown in Fig. 6. The cylinder liner bore should be 3.5001 inches. If wear or out of round is greater than .007 inch, replace cylinder liner as follows:
1. Using service tool 49 0636 015 and a suitable press, drive liner out of cylinder block bore toward deck side of block.
2. Apply engine oil to cylinder block bore and outer surface of liner, then press new liner into bore. Make sure that liner protrudes .026-.031 inch above deck surface. Pressing force should not exceed 6,600 lbs. If pressing force exceeds limits, find and correct cause of fitting problem.
3. Check that cylinder liner bore is within specifications.

PISTON INSPECTION

Visually inspect piston for scores, deep scratches or heat damage. Replace, if necessary. Measure piston diameter at top of skirt and perpendicular to piston pin with a micrometer. Piston diameter should be 3.4989 ±.0005 inch. If diameter is not within specifications, replace piston.

PISTON TO LINER CLEARANCE

Measure piston diameter and cylinder liner bore as outlined previously. Compare measurements. Piston to liner clearance should be .0021-.0031 inch. If clearance exceeds specifications, replace piston or cylinder liner.

PISTON RING GROOVE INSPECTION

Remove carbon from ring groove by using a ring groove cleaner or a broken piece of ring. Using a feeler gauge, check piston ring to groove side clearance. Side clearance limit is .012 inch. If side clearance is greater than specified limit, replace piston ring.

CHECKING PISTON RING END GAP

Place the piston ring in the cylinder bore below the ring travel, using a piston head to push the ring in squarely. Check the piston ring end gap with a feeler gauge. The end gap should be .015-.021 inch for the top ring, .011-.016 for second ring and .013-.021 inch for oil ring.

CHECKING PISTON PIN FIT

Check the clearance between the piston and the connecting rod small end bushing. Maximum allowable clearance is .0020 inch. If clearance exceeds specifications, replace the piston pin or small end bushing.

REPLACING CONNECTING ROD SMALL END BUSHING

1. Press out old bushing with a suitable mandrel.
2. Press fit the new bushing into the connecting rod, making sure oil holes in bushing and connecting rod are in alignment.
3. Finish the new bushing with a reamer to the desired clearance.

CONNECTING ROD BEARING

Visually inspect the connecting rod bearing for peeling, deep scores or heat damage. Replace, if necessary.

CHECKING CONNECTING ROD BEARING CLEARANCE

The connecting rod bearing clearance should be .0014-.0030 inch. Check the clearance by using Plastigage as follows:
1. Clean the surfaces of the bearing and crankpin.
2. Position a piece of Plastigage on the crankpin, then install the bearing cap and torque to specifications.
3. Remove the bearing cap and measure the width of the Plastigage. Compare width of Plastigage with the scale printed on the Plastigage envelope.

CHECKING CONNECTING ROD SIDE CLEARANCE

Check connecting rod side clearance with a feeler gauge. Side clearance should be .009-.013 inch. If side clearance is beyond specifications, replace connecting rod.

CHECKING CONNECTING ROD TWIST

Check the connecting rod for bend or twist by using a suitable connecting rod aligner. Maximum allowable twist is .002 inch per 3.9371 inches of rod. Repair, if necessary.

CHECKING CRANKSHAFT MAIN JOURNAL & CRANKPIN

Clean the crankshaft thoroughly with a suitable solvent and blow out the oil passages with compressed air. Inspect the crankshaft for cracks or scratches and the oil passages for clogs. Measure diameter of each crankpin and main journal with a micrometer. If the wear is more than 0.0020 in. (0.05 mm), the crankshaft should be ground to the undersize of 0.010, 0.020 and 0.030 in. (0.25, 0.50 and 0.75 mm). Refer to specifications for standard diameters of crankpins and main journals.

CHECKING CRANKSHAFT RUNOUT

To check runout, mount the crankshaft on the V-blocks and install a dial indicator. Slowly rotate the crankshaft and note the reading on the dial indicator. The maximum allowable runout is .0019 inch. If necessary, correct with a press.

MAIN BEARING

Visually inspect main bearing for peeling, deep scores or heat damage. Replace, if necessary.

CHECKING MAIN BEARING CLEARANCE

The main bearing clearance should be .0016-.0036 inch. Check the clearance by using Plastigage as follows:
1. Clean the surfaces of the bearing and main journal.
2. Position a piece of Plastigage on the main journal, then install the bearing cap and torque to specifications.
3. Remove the bearing cap and measure the width of the Plastigage. Compare width of Plastigage with the scale printed on the Plastigage envelope.

CHECKING CRANKSHAFT ENDPLAY

The end thrust of the crankshaft is taken by the thrust washers at the #3 main bearing. The standard endplay should be .0055-.0153 inch.
To measure crankshaft endplay, mount a dial indicator at rear of crankshaft, then move shaft fore and aft. Observe reading. If endplay is beyond specifications, replace thrust washer with available oversize washer.

CAMSHAFT INSPECTION

Visually inspect lobes and journals for scoring, wear or heat damage. Measure cam lift with a micrometer and, if not within specifications, replace camshaft. If cam journals are worn greater than .0003 inch, replace camshaft.

CHECKING CAMSHAFT RUNOUT

To check runout, mount camshaft in V-blocks, then install dial indicator and rotate camshaft. The maximum allowable runout is .0003 inch. If runout exceeds limit, replace camshaft.

CHECKING CAMSHAFT ENDPLAY

Fig. 7 Measuring camshaft endplay:

The endplay of the camshaft is determined by the clearance between the sprocket surface and the thrust plate surface. Measure this clearance with a feeler gauge as shown in Fig. 7. This clearance should be .0008-.0071 inch. If the endplay is excessive, replace with a new thrust plate.

CHECKING CAMSHAFT BEARING CLEARANCE

Using suitable micrometers, measure camshaft journal outside diameter and camshaft bearing inner diameter. Compare measurements. Maximum allowable bearing clearance is .0057 inch. If bearing clearance exceeds specifications, replace camshaft or cylinder block.

GEAR INSPECTION

Visually inspect gears for cracks, damage or missing teeth. Replace, if necessary.

CHECKING GEAR BACKLASH

Fig. 8 Measuring gear backlash:

Mount a dial indicator to gear being checked, then move gear clockwise and counterclockwise, Fig. 8. The maximum allowable gear backlash is .0118 inch. If backlash exceeds allowable limit, replace gear(s).

CHECKING IDLER GEAR ENDPLAY

Measure endplay with feeler gauge positioned between the gear and thrust plate. Gear endplay should be .0079-.0118 inch. If endplay exceeds specifications, replace thrust plate or gear.

CHECKING IDLER GEAR OIL CLEARANCE

Fig. 9 Checking idler gear oil clearance:

Measure inner diameter of idler gear bushing and outer diameter of spindle, Fig. 9. Compare measurements. The maximum allowable oil clearance is .0059 inch. If clearance exceeds allowable limit, replace idler gear bushing. To replace idler gear bushing, proceed as follows:
1. Using a suitable mandrel, press bushing from idler gear.
2. Press in new bushing using suitable mandrel.
3. Using a suitable reamer, ream bushing to desired fit.