2.8D cambelt tension


Hi Folks, I'm just fitting a new cambelt to my 89' 2.8d swb hard top. I'm struggling to get the cambelt to the right tension, Can anyone tell me how tight it should be (I've managed to get it so there is about 8mm up and down but this seem loose to me. Is there a tool to tension the belt?
Many Thanks, Chris.

No tool, so far as I know.

8mm on the longest run seems OK. I've done two 4trak belts and various other vehicles in my time and work on the basis of; 'if you twang it, and it plays a lowish tune, then it's tight enough'. I haven't had any breakages (yet).