Abstract: A petrol, internal combustion engine has, at transitions between an inlet manifold and inlet ports of a cylinder head, respective relatively rigid permeable disintegrators which re-atomize the petrol particles passing through them en route to the cylinders. Each disintegrator presents to the approaching mixture an exposed area covered with sharp-edged small holes extending through the disintegrator. Each disintegrator is made by plating a reticulated polyurethane foam with nickel-chrome alloy and then removing the plastics by heating in a vacuum furnace.