This is my attempt at doing the ultimate TBI modifications listed on this great site. Good for 50cfm of additional air flow which is fine on the 4.3L and the v8’s with STOCK TBI heads.  V8 engines with Head upgrades need the bored throttle bodies or you will lose power you paid for with those heads. Stock TBI unit flows 450cfm and that maxes out at around 250hp. These ultimate mods increases flow to 500cfm which maxes out at 275hp before it starts restricting power. Even a 383 with TBI heads will typically max out at around 280hp which is why I posted that head upgrades needs a bored throttle body which will flow 600+cfm.

http://www.thirdgen.org/newdesign/tech/ultimatetbi2.shtml

Next I ground down the ridge around the top of the throttle body until the top of the TBI is nice and flat.

I then ground down the throttle shafts by 50%.  The photos are of one side so that you can compare to the stock side. I used a Dremel tool with a carbide tip in it to do the grinding.

Lastly, I polished the throttle bores.  Some say polish some say don’t.  Mine didn’t look too hot so I opted for the polish.

So that is the ultimate TBI mods and it took me a little over an hour to accomplish.