Because of the demanding task and the special tools and equipment used, such work as reconditioning the valves, valve seats and the valve guides, usually known as the valve job, should be done by a professional. A home mechanic can unbolt the head, tidy it up and take it to a dealer service department or an automotive machine shop for the actual work to be done. The carrying out of the inspection enables one to have an evaluation of the state of affairs of the head and valve train parts as well as be aware of the jobs that are required in interacting with automotive machine shops where new parts might be needed. Lifting the valves and spring is done at the dealer service department or automotive machine shop and reconditioning or replacing the valve and valve seats, reconditioning of the guides, examination and replacements of the valve springs, spring retainers, and keepers if necessary, replacement of the valve seals with the new ones, assembling of the valves and ensuring the right installed spring height. Also, if the cylinder head gasket surface is distorted, it will be machined because a distorted surface is unfit for sealing. After its finishing and after a professional performs a valve job, the head will be as if it was newly made. On return it is necessary to wash off the head again in order to remove any metal scrap and abrasive dorsal which may be left from the valve squaring or from the milling and facing operations respectively and to blow out all oil holes and passages with compressed air if possible.