Q: Is servicing valves, valve seats, and valve guides best handled by an automotive machine shop on Nissan 300ZX?A: Because of the aggravating circumstances and due to the fact that specialized tools and equipments are needed to perform the task, the procedure known as valve job which involves servicing the valves, valve seats, and valve guides is better performed by an automotive machine shop. An individual working at home can take out the head, provide preliminary washing, and inspection, then take the head to a dealer service department or automotive machine shop for actual valve work. Perhaps, the shop will rebuild or replace the valves and valve seats, do the valve guides' reconditioning, check and replace the valve springs and their retainers and keepers as needed, replace valve guide seals, assemble the valves, and adjust the installed spring height. Also, if warped, the cylinder head gasket surface shall be refinished to flatness before the gasket is installed. After that, the head should be clean once more to remove any final traces of metal particles and abrasive grits issuing from the valve service and head resurfacing functions; one must employ compressed air if possible to blow out all the oil holes and passages.