The valves can be true but lots if the timing is to advanced on the distributor it wouls also result in a valve clatter noise. Valve Train noise if the adjustment is off and need to be set its even heard and best heard at IDLE if the noise is not heard at idle the first thing i would do is check the position of the distributor and see if its advanced to much, being to much advance will cause valvetrain clatter in low load ranges of 1000-2000