Because of the complex nature of the job and the special tools and equipment needed, servicing the valves, valve seats, and valve guides, commonly known as a valve job, is best left to a professional. The home mechanic can remove and disassemble the head, perform the initial cleaning and inspection, and then reassemble and deliver the head to a dealer service department or an automotive machine shop for the actual valve servicing. The dealer service department or automotive machine shop will remove the valves and springs, recondition or replace the valves and valve seats, recondition the valve guides, check and replace the valve springs, spring retainers, and keepers as necessary, replace the valve guide seals, reassemble the valve components, and ensure the installed spring height is correct. The cylinder head gasket surface will also be resurfaced if it is warped. After the valve job has been performed by a professional, the head will be in like new condition. When the head is returned, it is important to clean it again just before installation to remove any metal particles and abrasive grit that may still be present from the valve service or head resurfacing operations, using compressed air if available to blow out all the oil holes and passages.