I just finished a Groove job on a Chevy Vortec 4.3 V6 for a Chevy Silverado pickup. This is for my customer and new Forum member Herbert. I'll describe in detail the Groove and the Idle Air Control fill and restriction.
First this TB has the same throttle bore diameter as the DBW 5.3 V8 Vortec, I show them side by side to compare. Seems a big TB for 4.3 Liters to me! In one of my pics you will see a darker gray band visible just above the throttle plate, this is a concave radius. So if the bit is placed flat to the blade, it has a wrong angle to cut the Groove. This meant I had to judge and elevate the Dremel some to compensate for this. This put the cutting edge of bit a few millimeters away from the plate/bore intersection, and made it a bit tricky to cut this Groove. I got my usual Cave-Man looking Groove, but I've done uglier Grooves that have given great results before.
The other thing I did here was to fill in the huge IAC air inlet duct with regular JB Weld epoxy. I took a piece of hose and put a clear shiny box tape wrap on the hose so the JB wouldn't stick to it. The hose fit snug into the IAC valve's bore that intersects with the inlet duct. This allowed to fill the duct completely in two stages. I scratched up the duct surface to promote epoxy adhesion. For the first stage I put another piece of the clear box tape across the lower half of the duct opening to give a dam to fill epoxy against, this gave a smooth finish to the lower part of the fill closely matching the bore shape. This also left a ridge of JB sticking out that I used to fill in against for the second stage. I over filled the duct above the bore walls, then used a cylinder stone in a die grinder to rough cut down the cured JB Weld. Finished by hand with fine sandpaper. Then drilled two air holes through the epoxy, aimed and connecting to the IAC valve bore.
Two reasons to do this. Ron taught to restrict but not fully block IAC air, as many IAC valves never fully close, and so act as a manifold vacuum leak. IAC is an important function, but many TB's have massive IAC passages, so I use different ways to restrict them. This TB has that huge rectangular inlet duct cast into the bore wall, I think it can disrupt the surface air flow that sticks to the bore wall, and almost over the bore center. IT's almost right over the critical center 25% of the Groove's length. By filling and drilling this duct, I'm killing 2 birds with one stone.
You can see where I back filled w/ JB Quick in the thin area of the bore where the IAC dumps into the matching intake man. passage. The bit did break thru into the epoxy but not all the way through it. Best to back fill thin areas before Grooving, IMHO.
Tracy G.
Here's the pics:
