After hurricane Xantippe battered his store, the wholesale grocer, who had survived 23 hurricanes intact, found that he had only 4 pairs of weights and a balance scale left undamaged. With those 4 parts, luckily enough, he could weigh anything from 1 to 170 pounds. What were the 4 pairs of weights?

generally, the weights are powers of 3.

Are the pairs individual, so there are 8 weights in all?