I see that Cylinder Head Abrasives lists a series of high-helix carbides (http://www.ruffstuff.com/pages/high.html) and was interested in knowing if anyone here has tried them. I was considering one of the long-shank / flame-shaped in 1/2" or bigger for doing some "deep" intake manifold runner work, but don't want to drop the $$$ on it if it's not much of an improvement over traditional designs.

i use mine all the time. for a novice they take some getting used to though, they can be somewhat unstable and the longer the shank the more unstable they can get. you can remove a lot of material in a hurry, so you need to be careful.

I have some of the aggressive alumi-cut burrs on 4"-6" shanks now and was thinking (hoping?) the high-helix style might be more stable. Those things can go from "Wow!" to "Whoa!!!" in no time, as I suspect you know already.