blowing fuses in distribution block?

all of my fuses are blowing in my distribution block when i turn my stereo on. it is a stinger block with two 4 gauge wires in and four 8's out. the biggest amp fuse i could find was 30 amp. those are the only ones i could find to fit. the amps have about 4000 watts. are the fuses too small to handle the power, which i dont beleive or is it usually a short somewhere and if so where the wires to the batteries are less than 3 feet long and have no marks on them. any input will be appreciated and thanks.