Short answer - no, you can't just "double" the measurements.
You have to remove hte 1/4" seam allowance on all sides, then double, then add it back. For example, a 4-patch made of 4 3" squares (3.5" cut) to make a 6" block would be made from 4 6.5" blocks, not 7" blocks, to make a 12" finished square.
If you post the block, I'm sure someone on here can help you out, if you aren't comfortable redrafting it yourself.