X-Head Porting....

One other thing I do in some situations, when using a long burr, is to grab a 7mm valve guide and slip it over the shank and use it as a "handle" to help control it when it wants to grab. I put a little oil on it, but it still will get pretty hot. Sometimes there isn't enough room to use it, but it helps when I can. I can't remember the OD, but it is smaller than the common .502.
.427 or so I think. I don't mess with many import heads.