SPACER 1.00 in.(2.54 cm) long 9D1571 - Caterpillar

When inspecting the valve rotators, protective glasses or face shield and protective clothing must be worn, to help prevent being burned by hot oil or spray.
Engine valve rotators rotate the valves when the engine runs. This action helps to prevent deposits from building up on the valves and the valve seats.Perform the following steps after the engine valve lash is set, but before the valve covers are installed:
Start the engine according to Operation and Maintenance Manual, "Engine Starting" (Operation Section) for the procedure.
Operate the engine at low idle. Refer to Operation and Maintenance Manual, "Operator Controls".
Observe the top surface of each valve rotator. The valve rotators should turn slightly when the valves close.
A valve rotator which does not operate properly will accelerate valve face wear and valve seat wear and shorten valve life. If a damaged rotator is not replaced, valve face guttering could result and cause pieces of the valve to fall into the cylinder. This can cause piston and cylinder head damage.
If a valve fails to rotate, consult your Caterpillar dealer.