Recently installed a dual master power drum brake conversion on my 1966 mustang from NPD. Pedal travel is about 4". Pedal effort is not much less than when it was manual brakes. Engine supplies 17-18" of vacuum. Booster tests good. Is this a normal amount of travel?

 

Is this the straight shaft, no bellcrank "modern" booster? If so, that's about normal for them. They aren't very good. The OEM type, which is available, is much better.