I have read an article on drilling brake drums in Custom Rodder a while back, and acording to the article it actually does help braking. Besides the cooling affect it has on the drums, it allows built up gasses crated by the pads to escape from the drum. They say that the gasses from melting particulate on the pads actually creates a type of air pocket between the pad and the drum. You are actually compressing this before you make contact with the drum. Not sure if this is a bunch of crap, but the writer swears it made a huge improvement on his ealy 50's Dodge, braking ability.
Rob
I love the smell of burning rubber in the morning!