A variable cam engine is provided with a plurality of cams which open and close an intake valve and an exhaust valve, a cam change-over mechanism which changes over these cams according to the rise of the supplied oil pressure, a lubrication path which supplies lubricating oil discharged by an oil pump to the engine parts, and an oil pressure path which supplies part of this oil to the cam change-over mechanism. A throttle is provided in the lubrication path. By throttling this throttle in the low engine speed region, the oil pressure in the oil pressure path is maintained and the cams can be changed over by the change-over mechanism even when the engine is running at a low speed of, for example, 2500 rpm.