BOSS 6S8948 - Caterpillar

Illustration 1 g01330811
Cylinder and valve location
(A) Exhaust valve
(B) Inlet valve If the valve lash requires adjustment several times in a short period of time, excessive wear exists in a different part of the engine. Find the problem and make necessary repairs in order to prevent more damage to the engine.Not enough valve lash can be the cause of rapid wear of the camshaft and valve lifters. Not enough valve lash can indicate that the seats for the valves are worn.Valves become worn due to the following causes:
Fuel injection nozzles that operate incorrectly
Excessive dirt and oil are present on the filters for the inlet air.
The load capacity of the engine is frequently exceeded.Too much valve lash can cause broken valve stems, springs, and spring retainers. This will produce emissions in excess of the correct specification. There will also be a loss of engine power.Too much valve lash can be an indication of the following problems:
Worn camshaft and valve lifters
Worn rocker arms
Bent pushrods
Broken socket on the upper end of a pushrod
Loose adjustment screw for the valve lashIf the camshaft and valve lifters show rapid wear, look for fuel in the lubrication oil or dirty lubrication oil as a possible cause.Valve Lash Check
An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. Check the valve lash while the engine is stopped. The temperature of the engine does not change the valve lash setting.If the measurement is not within the acceptable clearance, adjustment is necessary. Refer to "Valve Lash Adjustment".Valve Lash Adjustment
It is very important to follow this valve lash adjustment procedure. Do not use the traditional opposing cylinders method. Failure to follow the correct procedure may result in serious engine damage.
Note: The procedure to adjust the engine valve lash for the C4.4 engine is different from conventional engines, due to the altered valve opening and closing events.
Table 2
Exhaust Valves Inlet Valves
Valve Lash 0.35 0.05 mm (0.0138 0.0020 inch) 0.35 0.05 mm (0.0138 0.0020 inch)
Firing Order 1-3-4-2(2)
(2) The No. 1 Cylinder is at the front of the engine.Note: For new engines, the valve lash should be checked and reset after the first 500 hours and after the next 500 hours. The valve lash will then be checked at service intervals of 1000 hours.Note: For example, if the pushrods in a remanufactured engine have been replaced with new parts then Adjust the valve lash to 0.25 0.05 mm (0.0098 0.0020 inch) for the initial rebuild. The tappets should be reset to 0.35 0.05 mm (0.0138 0.0020 inch) at the normal service intervals thereafter.
Illustration 2 g01336213
Setting the valve lash
(A) Angled feeler gauge
(1) Adjustment screw
(2) Locking screw
Accidental engine starting can cause injury or death to personnel.To prevent accidental engine starting, turn the ignition switch to the OFF position and place a do not operate tag at the ignition switch location.
Illustration 3 g01336214
Remove the valve mechanism cover. Refer to Disassembly and Assembly, "Valve Mechanism Cover - Remove and Install" for the removal procedure.