The holes need to be drilled at a slight angle to make sure they intersect the proper cooling passage. Straight drilling only allows about half the diameter of some of the holes to flow coolant.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!