when should a timing belt be changed on a 95 351?

 

actually it uses a chain-and as far as I know there is no set interval -i have checked them by grabbing the lower pulley and check by turning the lower pulley left to right up and down depends on how you look at it-the amount of slack should not be that muck less than a 1/4 of and inch-you sometimes have to remove the belt to do this-1/4 each way should be okay