Other mechanisms can be used in place of valve springs to keep the valves closed: Formula 1 engines employ pneumatic valve springs in which pneumatic pressure closes the valves, while motorcycle manufacturer Ducati uses desmodromic a system to mechanically close the valves.
This design had an exposed valvetrain (you could see the pushrods and lifters from the top) with nickel-plated rocker cover, an aluminum water-cooled intake manifold; the starter is in the valley, as is the gear driven generator with the fan clutch coming off of it.
Like many DOHC engines, this engine has an interference valvetrain design, making periodic timing belt changes vital to the