100mm TB???

Definitely a typo. The largest throttle body available for an LS1 is the 94mm that we carry. That won't bolt up to the factory intake, but will to some of the aftermarket units as well as our twin-screw supercharger set-up. There's really no reason to go above an 80mm on the stock intake due to the size of the mouth of the intake. On LTx motors 54mm was the largest you could go. For the 58mm throttle bodies you had to bore the front of the manifold, and for the mono-blades you had to port machine/match. You can't do that with the nylon intake, particularly because of the EGR design. The shape of the gasket, even on the non-egr LS1/6s limits the bore capability even if you do figure out a way to sucessfully machine the nylon.

I know the BBK's are a waste of money, but going to the 90mm TB with the 90mm LSX Intake will be nice for big motors. If it isnt a typo then there is a new GM intake.

Nope, it's definitely a typo. There is just no way to make a 100mm TB low-end and emissions friendly....aside from the fact that I'm familiar w/ the ins and outs of the entire Monaro/GTO platform. We had the intake off the test-car we had last month...regular old factory TB....The HSV TB is an 85 mm I believe???possibly 80.

I was just gonna say, I thought ours was 75.

I would only recommend one if you were keeping it strictly a bolt on car and had the cash to spend. When you start going heads, cam, blower, turbo, the stock MAF and TB simply work the best for tuning.

Interestingly, the fancy brochure you get mailed from GM to thank you for purchasing a GTO lists the 100mm TB specifically in the description of the LS1. I thought it was odd to have one that big, too..............

Guys, they are listing the outside diameter of the throttle body, it is indeed 4inch(100mm). The butterfly of course is only 78mm. If you pull the inlet tube off the throttle body, you will see what I mean, its starts out really large and then necks down to the butterfly.

The stock GTO TB is 75mm and so is the intake. The 78mm aftermarket TBs will bolt up but the full effect is lost due to the opening in the stock intake being only 75mm.

LT1Brutus said:

...as well as our twin-screw supercharger set-up...

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For the LS-1? This could be a whole nother thread.

ronaldvetteron said:

Interestingly, the fancy brochure you get mailed from GM to thank you for purchasing a GTO lists the 100mm TB specifically in the description of the LS1. I thought it was odd to have one that big, too..............

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No it doesn't. It says the PLENUM is 100mm. That's what R&T is talking about, too.

-Chris

DevilYellow said:

According to road and track the GTO has a 100mm throttle body.... some how I really doubt that

Well they say intake opening. A stock LS1/LS6 TB is 75, BBK is 80 with a reducer plate...there is a 90mm LSX intake coming out ....

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The GTO retains the LS1's 73mm throttle body, which is reused along with the MAF sensor in the MagnaCharger conversion process.

~73mm unported, get rid of that lip 75mm

I have found several places stating the above. Which makes sense when you see ads fro 75mm poirted and polished TBs for sale. If it was already 75mm, how could you port something to the exact same size? Polish yes, port no. Has anyone actually taken an inside micrometer and measured this yet for arguments sake?

Baaa said:

..... Has anyone actually taken an inside micrometer and measured this yet for arguments sake?

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Yes, I have. The stock GTO TB is 75mm and so is the intake manifold opening.

Just to throw another number into the mix, on pontiac.com they say the 2005 has a "newly enlarged 90 mm (3.5 inch!) air inlet". From the picture it does look like it necks down at the throttle plate.

According to the TB porting gurus (Jantzer, Bauer, Shaner, etc.) the stock TB blade/port is 75mm, as well as the intake opening. The TB itself necks down to 70mm before it reaches the blade. These guys port the TB openings to match the blade at 75mm. They also fill in the EGR cutouts with epoxy to smooth out the airflow.