You can't "increase the peak" so to speak on your biceps (hey, that rhymes).
Peak is genetic.
I used to have the same problem, bro, where my front delts overpowered my biceps. This was due to improper biceps training for years. You need to lower the weight and make sure you are squeezing the weight up with your bi's on whatever ex. you're doing, and they'll be sure to grow. (....try FLEX curls)