Just thought I would spread around an ordeal I had about 5 years ago with a machine shop called Midwest Motorsports in Ames, Iowa. These fools installed valve guides and tapped the rocker stud holes for screw in studs, on my 67 289 heads. The heads were fine, but tired. Within a few hundred miles I had three bent pushrods. Got new pushrods, a few hundred miles, and again, more bent ones. After carefull measuring I discovered that the valves and rocker studs were not absolutely straight, which caused the rocker arms to ride crooked, thus bending the pushrods. The machine shop can't drill straight holes it turns out. They refused to correct the problem, and other shops didn't want to back me in small claims court since Midwest Motorsports is an important place it seems. Anyway, a warning to fellow Iowans. BTW, that shop specializes in Chevys.