Karl posted some inaccurate information, so I deleted his post. I want only the most accurate info shared.
Here's his post with my comments:
Two of the first grooves that I did, there was an obvious indication that the groove was in the right spot... just like blowing across the top of a coke bottle, it whistled.
Both of these were carburetors. What was different about them compared to most of the TB's is that the plate angle was more define, ie: 25-30 degrees compared to the electronic TB's where the plate angle is 13-17 degrees. You don't get the whistle with the Electronic TB's.
The carburetor was probably not set correctly. If I have not made myself clear, I will here and now. "Carburetors require some additional knowledge and skill. This is covered in the Certification Classes." The plate was (probably) not closed completely. Hence, the extreme angle.
And you are wrong about the electronic throttles. The 04 and later GM and Ford truck series and the later model Land Rovers have whistled. About one in twenty or thirty have set up whistles when I've grooved them.
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Markus,
I think if I were to do something like that, I would go the other way...
large bit to the outside, small bit in the middle..
Thinking about the air flow within the groove and the impact at the center point.
Another thought too, particularly with the Chevrolet TB with the sloped venturi wall
The groove is applied with a slight angle away from the TB to accommodate the slope of the wall and I'm wondering if chasing the pocket with the small bit perpendicular to the throttle plate might enhance the effect somewhat.
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I figure if it helps that's a plus, if it doesn't change anything... no harm no foul, if it takes away... Something to be said for JB Qwik.
Karl Fortner
Tacoma, Wa.
Gadgetman Tacoma
Karl, you are an amazing man. Please take some more time thinking before you post.
Ron
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