A method of assembling a fluid end includes inserting a valve through a bore of a housing of the fluid end and into an interior volume of the fluid end, inserting a valve cover into the bore such that the valve cover seals the bore, and coupling a lock cover to the housing, the lock cover positioned over the bore to prevent removal of the valve cover from the bore. When the lock cover is coupled to the housing, the lock cover does not apply a preload against the valve cover.