2 minute read
Caterpillar, 3161 Governor
VALVE CLEARANCE
Valve clearance (lash) is measured between the rocker arm and the bridge for the valves. All clearance measurements and adjustments must be made with the engine stopped, and with the valves FULLY CLOSED.
Valve Clearance Check
When the valve clearance is checked, adjustment is NOT NECESSARY if the measurement is in the range given in the chart for VALVE CLEARANCE CHECK: ENGINE STOPPED. However, it is the recommendation of Caterpillar that the valve clearance setting is to be made at the initial (first) 1000 service hours of operation, and every 3000 service hours thereafter.
VALVE CLEARANCE: ENGINE STOPPED
VALVES ACCEPTABLE CLEARANCE RANGE Intake 0.30 to 0.46 mm (.012 to .018 in.) Exhaust 0.68 to 0.84 mm (.027 to .033 in.)
If the measurement is not within this range, or if the service meter indication is at the specified interval, adjustment is necessary. See the subject VALVE CLEARANCE ADJUSTMENT.
Valve Clearance Adjustment
NOTICE Due to normal changes (break-in effects) of new or rebuilt engines, the recommended first interval for valve clearance setting is at 1000 service hours of engine operation.
Use the procedure that follows for adjustment of the valves:
1. Put No. 1 piston at top center (TC) position. Make reference to FINDING TOP CENTER POSITION FOR NO. 1 PISTON.
2. With No. 1 piston at top center position of the correct stroke, adjustment can be made to the valves as shown in the chart CRANKSHAFT POSITIONS FOR FUEL TIMING AND VALVE CLEARANCE SETTING.
NOTE: Before any actual adjustments are made, tap (hit lightly) each rocker arm (at top of adjustment screw) with a soft hammer to be sure that the lifter roller is seated against the camshaft base circle. 3. Loosen the locknut for the push rod adjustment screw. If there is not enough clearance for feeler gauge between rocker arm and bridge contact surface, turn the adjustment screw counterclockwise to increase the valve clearance.
VALVE CLEARANCE SETTING: ENGINE STOPPED
VALVES GUAGE DIMENSION Intake 0.28 mm (.015 in.) Exhaust 0.76 mm (.030 in.)
4. Put a feeler gauge of the correct dimension between the rocker arm and bridge contact surface. Turn the adjustment screw clockwise until the valve clearance is set to the specifications in the chart VALVE CLEARANCE SETTING: ENGINE STOPPED.
VALVE CLEARANCE ADJUSTMENT
5. After each adjustment, tighten the nut for the adjustment screw to a torque of 70 + 15 N-m (50 + 11 lb. ft.) and check the adjustment again.
TIGHTEN ADJUSTMENT SCREW LOCKNUT
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6. Remove the timing bolt and turn the flywheel 3600 in the direction of engine rotation. This will put No. 1 piston at top center (TC) position on the opposite stroke. Install the timing bolt in the flywheel.
7. With No. I piston at top center position of the opposite stroke, adjustment can be made to the remainder of the valves as shown in the chart CRANKSHAFT POSITIONS FOR FUEL TIMING AND VALVE CLEARANCE SETTING.
8. Repeat Steps 3, 4 and 5 for these valve adjustments.
9. Remove the timing bolt from the flywheel when all valve clearances have been adjusted.
