An eight cylinder engine includes cylinders that are fired at intervals corresponding to a crank angle of 90 degrees. The firing is conducted in four cylinders of each of first and second banks at uneven intervals. In a pair of cylinders of each of the banks in which the firing is consecutively conducted at an interval corresponding to a crank angle of 90 degrees, a central angle of an exhaust cam provided for one cylinder in which the firing is conducted later is larger than that of an exhaust cam provided for the other cylinder. In a pair of cylinders of each of the banks in which the firing is consecutively conducted at an interval corresponding to a crank angle of 270 degrees, a central angle of an exhaust cam provided for one cylinder in which the firing is conducted later is larger than that of an exhaust cam provided for the other cylinder.