In previous work, we have presented application of a model of the convolutional interleaver in turbo codes acting as a block interleaver through inserting a number of stuff bits equal to the number of interleaver memories at the end of each data block. In order to get better turbo codes performance, the interleaver with larger period, which increases the number of stuff bits and reduces effective channel bandwidth usage, has been suggested. In this paper, we introduce a modification to this interleaver improving turbo codes performance without increasing the interleaver period. This is carried out by increasing distance of adjacent bits that are positioned in original input bit stream in the interleaving procedure. Application of the modified interleaver in different turbo codes structures have been verified and results have been compared with those for the previously suggested interleaver.