Because of the kind of job involved and the tools, and equipment needed for the job including the servicing of the valves, valve seats, and the valve guides which is normally referred to as the valve job, should always be done by a professional mechanic. An individual working at home can unbolt it and take off the head(s), it is then possible for him to do initial washing and assessments on it and bolt it back before taking it to a dealer service department, or an automotive machine shop for the actual work to be done on it. Performance of the inspection enables determination of the state of the heads and other valve train parts, for recognition of the needed works and new parts when interacting with an automotive machine shop. The dealer service department or the automotive machine shop, will have the valves and springs pulled out, the valves and seats will either be reconditioned or replaced, the guides will be reconditioned, the springs, spring retainers and keepers will be inspected for replacement if necessary, the seals usually will be replaced with new ones, the reassembled valve components as well as checking to ensure that the keeper and installed spring height is correct. Also, if the cylinder head gasket surface is altered, then it will be reconditioned to rectify the problem of warping. When the valve job is done by a professional, the head or any number of heads will be rather like new. Before fitting them back on the engine after use, they should be cleaned again for the removal of any metal pieces and grit that may remain from valving service or head Squaring operations respectively and by use of a blast of compressed air if possible to clear all oil ways or passage.