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Discussion Starter #1
Hey guys, I have heard of a throttle body mod but never really paid attention to see what it was. I assume this is slightly boreing the TB out or something.....?

How hard is the mod to do or where can you have it done....?

Can it cause any problems or interfere with sensors......?

Would this interfere with fuel efficiency....? What type of improvement can it give you....?


Any info would be appreciated, thanks.....
 

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well if it's the one I'm thinking of then you need to grind part of the TB where the butterfly is. I believe there's a stop that prevents it from going a full 90 degrees. Also you can bore out the TB a little bit thinner to increase the interior size. Not worth it in my opinion since both only add power at the absolute top end of the RPM range.

The other thing is to port and polish the TB. No one I know of has done this but if I ever get an extra engine/TB to play with, I'll try it. Anyone can correct me if I"m wrong but I believe porting and polishing only does good in certain areas because eventually you DO want turbulent air to enter the cylinder so it mixes better with the fuel.

hope this helps
 

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sorry I just noticed I didn't try to answer your other questions. I don't think it will affect your sensors, their purpose is to relay info to the computer about what is going on, the computer should be able to make instant adjustments for any changes. If you do a mod though, you should reset the computer to be safe.

Also anything that makes your engine breathe easier should increase fuel economy AFAIK.
 

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Discussion Starter #4 (Edited)
Thanks for the info......

Would not adversely affect fuel mileage.....? Who could do this mod since I don't have time to do it myself.....? A carb shop or something?
 

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A carb shop *might* do the butterfly mod if you are very specific about what you want. They would probably charge you an arm and a leg though since it involves a lot of skilled labor and good tools.

The port and polish is about 10 times more work and requires people who know exactly what they are doing and very specific tools. Depending on what pieces you want done, and how much work overall, they might even eat up a whole die grinder just for your job.

Whatever you do be sure that you are very specific about what you want them to do, get it in writing, and make sure that they are willing to buy you a replacement in case they screw up.
 

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Modifying the throttle body is only by a few mm, so its not going to be crazy amounts larger, Ive never done it so I cannot say weather its good or bad, but I would not pay to have this done, if you were going to do it yourself it may be a fun saturday afternoon project.
 

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I am planning on doing the 70MM TB next weekend. I'll try to remember to take pictures as I work and will post them when I am finished.
 

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Ok here is the scoop:

The stock TB on the 3.2/3.5 L engines has a 68MM Butterfly in it. The TB before the butterfly is necked down to 62MM

If you bore out the TB to 68 MM straight though this will net a 18% increase in airflow potential. (remember area of a circle formulas)

There is no change required to the butterfly.

A shop can bore it out for you or if you have patience, it can be done at home with a Dremel and a metal cutting bit (not a grindstone they plug with the aluminum) Then use 120 grit sanding attachments and then 240 grit to get a nice finish then use some rubbing compound to shine it up.

This mod increases off the line and top end performance, but not much in the midrange.

I have done over 20 of the TB's so I have a clue. Sorry I do not modify them anymore.

Also 70MM would be impossibe straight through because the outside diameter of the TB where the intake connects is only 71 MM so there would not be enough metal there.
 

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Discussion Starter #9
Hey, again guys thanks for the info.........

Hmmmm, what about the 2.7L TB...... Is it different from the 3.2L/3.5L Stock Holley?

So it's recommended not to really do anything with the butterfly......

What are the proper specs to get for the 2.7L Throttlebody mod....?


Thanks guys......
 

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2 things to think about before you modify your TB , 1:this will definatley void any warranty on that part and maybe more 2: talk to Sppok r/t as if I recall he modified his Tb , and was having throttle sticking problems ,the mod may have not caused it but a word of caution.
 

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dodgeguy said:
2 things to think about before you modify your TB , 1:this will definatley void any warranty on that part and maybe more 2: talk to Sppok r/t as if I recall he modified his Tb , and was having throttle sticking problems ,the mod may have not caused it but a word of caution.
I believe spook had the problem before he modded his TB. As for the warranty, mine is gone. Besides, if you plan on doing this and keeping your warranty, just buy another TB to mod, and keep the regular one, just in case ;)
 

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dodgeguy said:
2 things to think about before you modify your TB , 1:this will definatley void any warranty on that part and maybe more 2: talk to Sppok r/t as if I recall he modified his Tb , and was having throttle sticking problems ,the mod may have not caused it but a word of caution.
There's not much to go wrong with the TB..........sensors at best. I can't imagine they even remove the TB to replace them. Unless the dealer removes the TB and looks real close, they'll probably not even notice.

This mod can in no way make your throttle stick.........remember you're increasing the opening. There will be lots of filings, so just make sure the TB is nice and clean before you put it back on.

The mod is really easy..........taking the TB off is a pain in the ass as it's pretty tight in there. Here's the steps I used:

1. Remove intake.
2. Remove throttle cables - they pretty much pop off when the throttle is full open.
3. Remove the 4 bolts (torx) holding the TB on.
4. The TB has a guide pin that's attached to a bracket. Loosen this bracket so it pivots back and allows you the remove the TB.
5. Disconnect the sensor wires.
 

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Discussion Starter #14
Cool, thanks to everyone for the info. I'll watch it monitor it closely to be safe, hopefully it'l be cool.

Again, should I mod mine for my 2.7L to the same specified mm??? Should there be other specs for the TB or is it the same.....?

Yeah, I may buy another just incase if I do have any problems.
 
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