A high pressure homogenizer provided with head for the treatment of products with solids and fibers comprises a block defining a passage for the product from an intake area to a delivery area, a piston movable axially with reciprocating motion in the block to pump the product in said passage, intake and delivery valves positioned internally to the block and operatively active on said passage to open it/close as a function of a motion of the products in the passage. The passage is positioned in the block in position of non-interference with the motion of the piston and the intake and delivery valves have no springs and are operatively inserted in said passage in intermediate position between said intake and delivery areas, to favor the sliding of the products and to prevent the accumulation of substances that are sensitive to shear effects contained in the products themselves.