TOPIC: '87 to '95 GM TBI Rerouting Idle Air Pathway

I've posted a supplement to the original "Rerouting the Idle Air Pathway" service bulletin which applies specifically to 1987 to 1995 GM TBI units on 350 and 305 engines. It may viewed in the document section at:

Welcome to Gadgetman Land! The Gadgetman Groove: The World's Best in Fuel Economy

It is the same process I used to enhance the Gadgetman Groove on my 1995 Chevy Suburban to gain 35% in fuel mileage.

Hey Nick, this is Aron Cheek Gadgetmannebraska. This is great information. I tried something similar the other day and this is the key to these tbi systems isn't it. Thank God for people who do not know the word impossible! I will call you sometime about a 2002 dodge 1500 , magnum engine map sensor vaccuum relocation. WORKS GREAT!!! Aron Cheek Gadgetmannebraska

Hey guys, I wanted to report a mod that I did this weekend following your pdf guidline...and with Tracy's help .

This was on a 94 model 350 (pics below). I grooved it first, then realized a week later that I needed to mod the Idle Air Passageway so pulled it back off and did the mod and added more groove.

The orange on some of the pictures is permanent marker, so you can see the contrast and the groove better.

I used a router attachment and router bit for my drimel and it worked really well for this application and I wanted to share it. I think that I may have made it a little too wide and deep but overall I'm super impressed with the workman ship that I produced using the router attachment.

That said, I still need to practice me grooving!


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WWAAHHH! your Grooves look good to me, Wayne. But the rest of the pic's aren't there!

Oh well, just try uploading again. Maybe the 'puters didn't like moving so many at once. Might try loading 4 at a time, add them as edits or just start another post we wanna see 'em!

Glad you're Groovin, Wayne, I enjoyed talkin' with ya!

Tracy G

TracyG wrote: WWAAHHH! your Grooves look good to me, Wayne. But the rest of the pic's aren't there!

Oh well, just try uploading again. Maybe the 'puters didn't like moving so many at once. Might try loading 4 at a time, add them as edits or just start another post we wanna see 'em!

Glad you're Groovin, Wayne, I enjoyed talkin' with ya!

Tracy G

Hey there Tracy, thanks for letting me know the pics didn't work, I moved them in PhotoBucked after I attached them so they were't at the same URL darn it!

Anyway, everything is fixed in the above post...thanks again!

Wayne
Gadgetman Carolinas

Hey Wayne, XCLNT work and Great pics! This post re-inforces the how-to of this mod. Just Beautiful contouring on all that IAC Trench work...man...! To me this is reference material for this Mod!

So how does it like it now, how does the IAC function modded like this?

I'd think it should get all the air it could want for any situation. Maybe Ron could weigh in on this one...

Would you describe exactly the type/size bit used w/ the router attachment?

Anyway, congrats on very Nice Work!

Thank you, Wayne!

Tracy G

TracyG wrote: Hey Wayne, XCLNT work and Great pics! This post re-inforces the how-to of this mod. Just Beautiful contouring on all that IAC Trench work...man...! To me this is reference material for this Mod!

So how does it like it now, how does the IAC function modded like this?

I'd think it should get all the air it could want for any situation. Maybe Ron could weigh in on this one...

Would you describe exactly the type/size bit used w/ the router attachment?

Anyway, congrats on very Nice Work!

Thank you, Wayne!

Tracy G

Thanks Tracy for all of the props and kind words!

I'm not sure what the size of the bit is but it's an end/mill style of a router bit. Not sure though...but I will look at it tomorrow.

Performance wise, I only slightly had to adjust the idle which leads me to believe that I should have made it slightly smaller and relied on the butterfly valve to let in more air rather than the IAC bypass. So next time I would cut it slightly more shallow or now quite as wide.

The orange marker was simply because I though that it'd show up in pictures better if I colored it. hehe

Wayne, SC
Gadgetman Carolinas

Hi Guys,
I am new to Gadgetland. I am preparing to groove my personal ride. Its a 1991 Chevy pickup with a 350 TBI motor. Can you tell me where the link is that has the pics of the moded TBI?

Hi Counterman! Welcome to GadgetmanLand!

Who Dat and where ya At?

OK- go to top of this thread, click link in Nick's orig. post. Or once in the forum, click Index top left corner. Go to Service Bulletins, you will find info there. I say that Wayne's post on this w/ his pics is refernce material as well, but Nick's info has more detail.

You can see that when people post good pics of their work and share detail, it grows our collective info base. That's how we all improve.

Tracy G

Hi Wayne, thanks to you I checked the box my Dremel came in, discovered a router attachment came w/ it. I think just a dremel small ball end mill cutter would work? The cuttter you used can cut deeper/faster than a small ball end one, and helped give those beautiful smooth trenches. Maybe a small ball end one would give a narrow shallower trench depending on depth adjustment.

Just typing out loud.

Tracy G

TracyG wrote: Hi Wayne, thanks to you I checked the box my Dremel came in, discovered a router attachment came w/ it. I think just a dremel small ball end mill cutter would work? The cuttter you used can cut deeper/faster than a small ball end one, and helped give those beautiful smooth trenches. Maybe a small ball end one would give a narrow shallower trench depending on depth adjustment.

Just typing out loud.

Tracy G

Hola!

Thinking out loud is the way to go brotha!

Umm, I wouldn't really want to use the rounded burr bit because I like the nice clean neat edge that that this bit leaves. Also, it was nice to be able to use the aluminum on the one side sort-of as a guide. I will also add, the bit that I used is slightly more than half the width of the trench so I could have left is much narrower, I just chose to make it bigger and I chose to set the depth a little deeper too. I can always go back and fill in and re-cut but I don't think it's gonna be necessary.

If I was to do it again, I would cut the width back by about 1/3 (of what I cut as a whole) and I'd make it about a millimeter shallower. I used a piece of board to set the depth too. Doing it this way eliminates the need for a steady hand!

Cheers, Wayne
Gadgetman Carolinas

Being new to this, I have a question. What is the purpose of changing the idle air pathway?