0308876 JOHNSON "O" RING CRANKCASE HEAD LOWER

Table 1
3500 and C175 Engines
Maintenance Intervals for Valve Bridge and Valve Lash Adjustment
Initial Interval Initial 250 Service Hours
Subsequent Interval Every 4000 Service Hours The initial adjustment of the valve bridge and valve lash is critical for new engines and for engines that have been overhauled. Tests have indicated that the settings change from the initial start-up through the first 100 hours of operation. The settings can continue to change during further operation. For this reason, adjust the valve bridge and the valve lash after the break-in period of the initial 250 operating hours.
Failure to perform the initial interval and/or the subsequent intervals will result in engine damage from these conditions: excessive exhaust temperatures, incorrect seating of the valves and contact between the valves and the piston.Incorrect adjustment of the valve bridge and/or of the valve lash can result in engine damage from these conditions: excessive exhaust temperatures, incorrect seating of the valves and contact between the valves and the piston.Incorrect lash maintenance can result in increased valve wear and can contribute to camshaft spalling.
Perform the initial adjustment for the following circumstances:
The engine is new.
The engine has been overhauled.
At least one of the engine cylinder heads has been serviced with a new valve train component.Note: Perform the initial adjustment even if an adjustment was performed after a dyno test or after the engine initial start-up.The engine tests have also indicated that valve bridge and valve lash settings are more stable after the break-in period. For this reason, adjust the valve bridge and the valve lash after every 4000 operating hours.Note: The initial 250 service hour adjustment of the valve bridge and valve lash enables the regular maintenance at every 4000 service hours until the engine is overhauled. If the initial 250 service hour adjustment is not performed, more frequent subsequent adjustment may be necessary.For instructions on adjusting the valve bridge and the valve lash, refer to the engine Systems Operation/Testing and Adjusting manual.Note: Make sure that you note the maintenance intervals in the machine Operation and Maintenance Manual, "Maintenance Interval Schedule". The maintenance intervals will be included in the Operation and Maintenance Manual when the manual is revised.
Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.
Perform the adjustment when the engine is cold. Before the adjustment is performed, the engine must be shut down for a minimum of 20 minutes. After shutdown and removal of the valve covers, the engine is considered cold because approximately 20 minutes are needed for removal of the valve covers.The valve bridge must be adjusted before the valve lash is checked and/or adjusted. Verify that both valve bridges for each cylinder are correct. Then measure the valve lash.If the valve lash is within 0.08 mm ( 0.003 inch) of the specification that is listed in Table 2, adjustment of the valve lash is not necessary. If the measurement is not within the tolerance, adjust the valve lash according to the specification that is listed in Table 2.
Table 2
3500 Engine Valve Lash
Valve Specification
Inlet 0.50 mm (0.020 inch)
Exhaust 1.00 mm (0.040 inch)
C175 Engine Valve Lash
Inlet 0.8 mm (0.03 inch)
Exhaust 1.3 mm (0.05 inch)