Check and Adjust Valve Lash-748G-III

causym CAUTION: To prevent accidental starting of engine while performing valve adjustments, always disconnect NEGATIVE (-) battery terminal.

IMPORTANT: Valve clearance MUST BE checked and adjusted with engine COLD.

1. Remove rocker arm cover with ventilator tube.

IMPORTANT: Visually inspect contact surfaces of valve tips and rocker arm wear pads. Check all parts for excessive wear, breakage, or cracks. Replace parts that show visible damage.

Rocker arms that exhibit excessive valve clearance should be inspected more thoroughly to identify damaged parts.

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2. Remove plastic plug from cylinder block bores and install JDE81-1 or JDG820 Flywheel Turning Tool (A) and JDE81-4 Timing Pin (B).

3. Rotate engine with the flywheel turning tool until timing pin engages timing hole in flywheel.

If the rocker arms for No. 1 (front) cylinder are loose, the engine is at No. 1 "TDC-Compression."

If the rocker arms for No. 6 (rear) cylinder are loose, the engine is at No. 6 "TDC-Compression." Rotate the engine one full revolution (360°) to No. 1 "TDC-Compression."

RG7013


A-Flywheel Turning Tool
B-Timing Pin

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4. With engine lock-pinned at "TDC" of No. 1 piston's compression stroke, check valve clearance on Nos. 1, 3, and 5 exhaust valves and Nos. 1, 2, and 4 intake valves.

Specification

748G-III Intake Valve (Rocker Arm-to-Valve Tip With Engine Cold) Checking -Clearance 0.41-0.51 mm
(0.016-0.020 in.)
748G-III Exhaust Valve (Rocker Arm-to-Valve Tip With Engine Cold) Checking -Clearance 0.66-0.76 mm
(0.026-0.030 in.)

5. Rotate flywheel 360° until No. 6 piston is at "TDC" of its compression stroke. Rocker arms for No. 6 piston should be loose.

6. Check valve clearance to the same specifications on Nos. 2, 4, and 6 exhaust and Nos. 3, 5, and 6 intake valves.

NOTE: Adjust valve clearance in the same sequence used for checking clearance.

7. If valve clearance needs to be adjusted, loosen the lock nut on rocker arm adjusting screw. Turn adjusting screw until feeler gauge slips with a slight drag. Hold the adjusting screw from turning with screwdriver and tighten lock nut to specifications.

Specification

748G-III Valve Adjusting Screw Lock Nut -Torque 27 N·m (20 lb-ft)
Recheck clearance again after tightening lock nut and compare to the following specifications. Readjust clearance as necessary.

Specification

748G-III Intake Valve (Rocker Arm-to-Valve Tip With Engine Cold) Adjustment -Clearance 0.46 mm (0.018-in.)
748G-III Exhaust Valve (Rocker Arm-to-Valve Tip With Engine Cold) Adjustment -Clearance 0.71 mm (0.028-in.)

8. Install rocker arm cover and tighten cap screws to specifications.

RG5241
RG4295

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Specification

748G-III Rocker Arm Cover-to-Cylinder Head Cap Screws -Torque 8 N·m (6 lb-ft) (72 lb-in.)

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