Bore out TB?

what exactly did he bore out? what sounded mean?

If you're reffering to boring out the stock plenum, then yes, it can be done. You can bore it out a bit with a dremel tool, but you really need a die grinder for best results. The hp gains are not huge, but worth it since its free power if you have the spare time and tools needed to do it. I think I'm going to do another "how to" write up for porting and polishing intakes and throttle bodies. I just don't know if enough people are interested for it to be worth it.

when I was doing my PI swap I noticed on my stock plenum that someone prior to me owning the car tried to and it has a big line of skip marks were someone attempted to port it. I have a dremel in my garage and free time today. What bits would I need to port it? And what to what to smooth it out well?

on a 4cyl?

Orions98GT said:

when I was doing my PI swap I noticed on my stock plenum that someone prior to me owning the car tried to and it has a big line of skip marks were someone attempted to port it. I have a dremel in my garage and free time today. What bits would I need to port it? And what to what to smooth it out well?

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What you need to do is find some bits and heads that are meant for grinding metal to remove larger amounts of surface material. There is an orange stone piece and some green ones I'm thinking of. They tend to work well, but I don't know their part number off the top of my head. Try to let the dremel tool do the work for you, rather than you doing the work yourself. Only in places where excessive material lies do you need to use extra pressure. Once you've grinded it down a bit, its time to smooth it out some. Using the sanding heads that Dremel makes will work great. Start with an 80 grit, then try the 120 grit. Again, try not to apply excessive pressure in one area more than another, unless if you need to remove more material in one spot. After you've grinded it down, and smoothed it out you can try using some sandpaper, or preferabley a sanding block to smooth it out. Go to the home improvement/building section of any good store and buy both a medium and fine grit sanding block. When I say medium grit, I mean around 120-180 grit. The fine sanding block should be no greater than a 250 grit, but you can get some as fine as 320 grit. Use the medium block, followed by the fine block. You should produce a really smooth finish. To finish, be sure to clean the piece up. Carb and choke cleaner works well. Spray out each of the surface holes, such as the ones for the IAC and EGR. You don't want any metal grit to be left when you install it and risk it getting sucked into the motor. If you wish, you can make it a bit smoother by using a nice metal polish, like mothers metal polish. I did this and made a mirror surface on the inside of mine. Though that can be time consuming.

Another option for polishing is to use dremel polishing compound with cotton heads, but its a little more tricky. If you apply even a bit much pressure in one area, it will produce a swirl effect in the surface of the metal. That, and when using a dremel tool inside the plenum, you run the risk of the choke scraping against the surface and putting a nice scratch in it. Its really up to you which route you want to take to polish it up. In the end, this can be a time consuming project. Depends on how far you want to go. I spent many hours working on mine. In the end, I got it to a flat and smooth finish that looked professionally done. I think it was worth it.

As for the throttle body, its not difficult at all to do. Best thing to do is to remove the throttle blade for easier polishing access. The stock casting isn't great, but definately not as rough as other surfaces. You should be able to polish up the throttle body by just using the sanding blocks I recommended above. A medium grit, followed by a fine gritt. When re-installing the throttle blade, be sure to get those screws tight. You do NOT want one falling loose and falling into the motor.

If you have any questions, just ask.

do you happen to have any before and after pics

thanks for the info, guess I will get started.

I'm sorry, I don't mean to sound like an ass but, your friend "bored" out a stock TB on a Saturn Ion and it made an other wise stock car sound... mean? On a 4cyl no less? Was it even a Saturn Ion Redline?

Also, on most throttle bodies, there's next to no "additional" material available to remove. Sure, you could probably open it up maybe 1-2mm's but, that'll do squat.

I've done my fair share of port and polishing, which can be placed in the same category as "boring" out a stock throttle body. Suffice to say, it's more of a - well, I did it because I could - kind of mod and had no real effect on the car, sound or performance wise. And this is on V8's.

By no means am I trying to throw a BS flag on you but, it sounds an awful lot like a turbonator story. Too good to be true. Maybe he has a healthy vacuum leak and his car is idling really rough.

EDIT: Sorry, double post.

Double post. My mistake. Apparently, my browser has a problem.

ALEX2028 said:

do you happen to have any before and after pics

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I would if the digital camera would have worked on this computer. I used to have some pics on here of my throttle body after I polished it up, but the thread was lost in the Stangnet crash. I guess if I ever port another upper intake, I'll have to be sure to get a digital camera that will work on this computer and take some pics. Speaking of which, that sounds like a good idea for another project.

BTW, I kinda agree with Redfire. I really don't see where boring out a throttle body is going to make any car have a "mean sound" to it, let alone a 4 cylinder. Now, maybe your friend bored out his throttle body and intake manifold or maybe he installed a cold air kit or something with it. That would cause a change in idle sound.

I've got a p&p stock upper took a few hours to do in my back to back gtech sessions I picked up 1mph in the quarter not huge but every little bit helps right.
As for the TB we used to do this on Fox's basically funneling the tb so it is only stock size by the blade we also used to mill the shaft down. Did no back to backs on those but the SOTP meter said it helped. Also if you do it be carefull if you remove too much around the blade it will make the car run like dog poo.

if you bore out your TB your car shouldn't run very good at all. If you remove the butterfly like suggested earlier, and take off much, it will be like a vacume leak.
if you just bore the front and rear , then you still have the same size opening for air to go through in the middle. As for sound, must be a Saturn thing.

forpit2000gt said:

if you bore out your TB your car shouldn't run very good at all. If you remove the butterfly like suggested earlier, and take off much, it will be like a vacume leak.
if you just bore the front and rear , then you still have the same size opening for air to go through in the middle. As for sound, must be a Saturn thing.

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Thats why I mainly used the term "polishing" when reffering to working over the throttle body. I also said to use medium and fine gritt sanding blocks, but not a dremel tool. The key is to make the surface of the throttle body smooth, and not to hollow it out. Indeed, removing too much surface space will result in an air leak and too high of an idle, which will throw IAC codes.

I guess people dont look at the TB..its FREEGIN smooth. "smoothing" it up wont do anything...in reality the groves you make in it wath sand paper will probably reduces flow. And like said, you cant make it any bigger because the blade will not sill, and if you make the rest of it bigger, it will hit the lip where it has to seal the blade and will also reduce flow......buy a BBK 75MM TB like I did. I was going to do the same thing until I was told about the blade sealing thing....and buy a TF plenum for $140...all cheaper and better castings.