Replacing Valve Seats

valve seats
(Valve seat) The valve seat in an internal combustion gasoline or diesel engine is the surface against which an intake or an exhaust valve rests during the portion of the engine operating cycle when that valve is closed.
(Valve Seat) That area of the quick-action coupling that comes in contact with either the ball or poppet valve, allowing a positive sealing surface. Shape and surface varies with valve style.

replacing
Take the place of
(replace) substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected); "He replaced the old razor blade"; "We need to replace the secretary that left a month ago"; "the insurance will replace the lost income"; "This antique
replacement: the act of furnishing an equivalent person or thing in the place of another; "replacing the star will not be easy"
Fill the role of (someone or something) with a substitute
Provide or find a substitute for (something that is broken, old, or inoperative)
(replace) supplant: take the place or move into the position of; "Smith replaced Miller as CEO after Miller left"; "the computer has supplanted the slide rule"; "Mary replaced Susan as the team's captain and the highest-ranked player in the school"