The NOS GM Chevelle front drum and original GM Chevelle front drums I have do not have flared pilot holes. The drums fit snug to the hub collar, and have zero side to side play on the hub. Two different after market drums I have/tried both have flared pilot holes. I Noticed that raised pilot hole (flared edge) sites slightly above the hub collar, and allows the drum to move side to side some. (no lug/tire installed . I have seen that flared pilot on rear drums. What is the purpose of a flared pilot hole in a front drum?

 

The 9 inch Chevrolet front drums, if I recall properly, are not attached to the wheel hub via swaged wheel studs as on other GM vehicles, probably a cost cutting measure. Thusly to maintain good concentricity with the hub they must fit snugly on the wheel hub center.