Yes esp. if the sound is only at high speed. Timing belt or more likely one of the idler pulleys. Maybe one of the valve spacers. It could be a exhaust pipe hitting something. Get a 3' piece of 1/2" wooden dowel. With your rig running just put the end of the stick in a spot on the motor then put your ear to the other end. If you've never done this you'll be amazed how clearly you can hear localized stuff in any area of the engine this way. Almost always if it's internal the sound is there at an idle too. It's just quieter.