Nate and Karl- you guys keep at it, I think you are both going to show us things in the time to come!
Yes Karl the double groove will certainly double your mileage, as long as you calculate in half-mile increments...and it always does this on the fifth Tuesday of every month, guar-un-tee'd...
That's not all, if you make the trip cross-country, I'll even show ya my secret method of rotating all 4 of your tires simultaneously, no need to go to the tire store...
Ok the guy with the long hook just jerked me off the stage...
Actually Karl ya got me slapping my forehead here...of course...it IS possible to move the Groove slightly downstream from the normal idle position with help of the idle set screw, dunno why I never thought of that...can't remember if Ron ever had much to say on that. Some analogy to Grooving the GM Vortec DBW TB's here, where if you get the Groove at too low of throttle angle it has, shall we say, Interesting results. Like a truck that won't idle at under 18 MPH- where the Owner lives next to/in a 15MPH Park speed zone!! (ask me why I know)
Nate I'll see If I can get the pic's of Karl's TB uploaded tomorrow, I'm too tired to do much right now. And Karl right you are about the Certified bits/program heck I could buy a Subaru I know of right now and still have 2 grand left... but it's all in the name of Progress and Adventure and Curiosity, right? But hey- I'm a guy who has fun w/ a Dremel and discovered tin snips a few years back...
One other thing- Karl in speaking of throttle angles and bit Groove cutting angles together, we may be confusing the issue possibly. Throttle angle is how many degrees of arc from fully closed (or maybe theoretically from a tangent position relative to bore centerline)a throttle is at. When Ron spoke of the 15-20 deg angle I think he referred to how far up from parallell to the bore wall the tool shaft is as it is held while cutting. Now- you could use an idle set screw to move a throttle plate to a certain angle, but in so doing you would be moving the Groove downstream if you were placing the flat end of bit against the plate as a backstop...I usually just look at the shaft taper just below the bit head, and try to get that taper about parallell to the bore wall. For those fastidious enough, get a cheap protractor from the school supply isle, and measure out the desired angle to some flat card stock and cut a template of the angle you wish. You can do this to a size to fit most any- or even to a certain TB in question. Then you have a guide to stick into the bore to give a visual of that angle as reference when cutting that Groove. Probably would work better for those with better vision than mine!
Ok that's enuf crazy detail for one evening...keep Grooving, make more aluminum dust!!
Tracy G