Usage:
3508 (7YG, 99W),
3508B (2GR),
3512 (4WJ, 96Z),
3512B (8BR),
3516 (2PK, 54Z),
3516B (7TR) Machine Engines
Reference: Service Magazine; July 11, 1994; Page 17; "Intake and Exhaust Valve Lash Increased"
Description of Change:
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Incorrect valve adjustment can result in engine damage from elevated exhaust temperatures, incorrect valve seating, or valve to piston interference..
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Improved valve lash and bridge adjustment intervals are used in the above engines for Caterpillar built machines.
Recent engine tests have shown the CRITICAL importance of the first valve lash and bridge adjustment. The tests show that the valve lash continues to change from start up through the first 100 hours or more of operation on a new or an overhauled 3500 or 3500B Engine.
After the initial "break-in" period, the amount of change in the valve lash is dramatically less. For this reason, valve lash and bridge adjustments after the first interval have been changed from every 2 000 hour to every 4 000 hours. See Chart 1 for the recommended interval for initial valve lash and bridge adjustments.
NOTE: If the initial valve lash and bridge adjustments are made as per Chart 1, see Chart 2 for the re-adjustment schedule. The re-adjustment schedule in Chart 2 can then be used throughout the life of the engine until overhaul.
Adaptable To: The valve lash settings in chart 3 are in effect with current production, and adaptable back to first production.
Bridge Adjustment
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- * The bridges MUST be adjusted before setting the valve lash. At each interval for setting the valve lash, start the process by adjusting the bridges first.
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- * After adjusting the bridges, measure the valve lash. If the valve lash is within ± .08 mm (.003 in) of the nominal valve lash in Chart 3, valve adjustment is not required. If the valve lash is not within these tolerances, set the valve lash as per Chart 3.
Setting The Valve Lash
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- * Refer to the machine service manual for the valve lash setting procedures. Valves and bridges can be set on a cold engine or on an engine that has been shut OFF for 20 minutes.
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- * If desired, valves can be set during an engine overhaul so that after the dyno test most if not all of the valves will fall within nominal specs and tolerances. See Charts 4 and 5.
