What is an auto head job?

An auto head job usually includes replacement of exhaust valves, machining of valves & seats, replacement of valve guides, valve stem seals, measuring and truing the deck surface if warped. The goal is to keep the valves moving straight, the head to seal against the block properly, and keep oil from being sucked into the combustion chamber. If anything is wrong in these areas you car will not run well at all.