Abstract: A closed enclosure for a vehicle engine has an air inlet and an air outlet formed at its front and rear ends. Both air inlet and air outlet have sets of sound absorber blades for noiselessly admitting ambient cooling air into the enclosure and for noiselessly exhausting the air therefrom. Disposed horizontally within the enclosure, a first heat insulating partition divides its interior into an engine compartment accommodating the engine and, thereover, a muffler and air cleaner compartment. A second heat insulating partition is mounted vertically on the first partition to subdivide the muffler and air cleaner compartment into a muffler compartment receiving an exhaust muffler assembly and an air cleaner compartment receiving an air cleaner assembly. The engine compartment is open both forwardly and rearwardly for the passage of the cooling air therethrough.