Disc brake help.

I have a 67 barracuda and we just put a disc brake conversion on it. I'm very happy with it but. While driving usually in town I here a noise up front in the brakes, if I lightly apply my foot to the brake it goes away and may stay away for 10-20 miles, it is very intermittent You never know when it will do it, brakes work great just this noise that's driving me crazy, and help or suggestions on what to do? Thanks in advance.