Low rpm noise in my voyager 96

HELLO!! I know that this forum is good and there are people who like to help, because they have similar vehicles and problems that have solved. Thank you all. Now the problem is as follows: My Voyaguer 96.3.2 of 6 cylinders is recently refined but they left me with about 700-800 r.pm. Vacuum march and this speed I hear a noise like a band skating inside the engine. By accelerating at 1000 rpm the noise disappears. I'm going to accelerate it because I don't like that noise, but I would like to know if someone has happened to someone and what is noise ... where they come because they are not external bands. Do you know what rpm that must be in empty?:

The turns should be between the 850 rpm do is minimal or when it makes that noise throw a little water to the straps if the foundocambia or it is possible to have the dry or crystallized straps.- Greetings Alf