http://minecraftbuildcraft.wikia.com/wiki/Quarry
FYI to correct some info I gave last night.
http://minecraftbuildcraft.wikia.com/wiki/Quarry
Quote2MJ/t is enough to keep a quarry continuously running, but a quarry will use up to 32MJ/t at maximum speed (increased from 9MJ/t previously). It therefore takes 8 combustion engines (48MJ/t) running on fuel to move the quarry head at full speed of 5.2m/s and provide the additional energy of 60MJ for each block broken.
Does it handle overflow? I can't remember.
I know some machines will explode if they overload with power (which is why luminators suck)
I don't belive they will overload. I had three of my fancy redstone energy cubes set up to give it up to 100mj/t each, and it was fine.