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Anyone 100% know off hand if the 75mm N* TB and the LS1 TB have the same mounting pattern?
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Can the 3500 plenum be opened up enough for a 75mm throttle? Those tbs use a throttle cable coming from the rear instead of the front, right?'89 Firebird, 3500 Turbo, T56, 9-bolt/4.11
'86 Fiero, 3500, 4-speed -
Yes, mine is ported to 75mm.
Yep, the LS1's are set up to pull towards the rear.Comment
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3500 UIM's can be bored out that big!? hmmm, LS1 TB and maf sitting on the shelf in the garage..."I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."Comment
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specifically:
if it's not identical, it sure is similar.Comment
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yah, that's kinda what i'm seeing too...
I know a guy that runs a shop doing LS conversions locally, i'll have to stop by with my adapter and see if one will fit. Maybe he'll hook me up too.. lolComment
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Can you port a 3400 out to that? Right now I have the 65mm. It seemed like a good idea for me since my charge pipe is 2.5ins but thinking about it, it would probably be better to use a bigger TB to give a better expansion into the intake. It would be more of a funnel then from 2.5in pipe, 3in tb, then the intake size instead of a straw to a container lol.Comment
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You can see it gets pretty close on the 3500 UIM, still good enough for the O ring to seal on the adapter.
I don't think you can go that far with a 3400 UIM, i don't have any to check against though.
I'm trying to find a LS throttle body locally, no luck yet though..Attached FilesComment
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The answer is Yes, the 75mm Silverado 5.3/ LS1 type throttle body bolts to the adapter perfectly.
The only issues are the IAC air passage, easy fix is to hog out a channel in the TB for it. And the fact that the LS plenum has the Oring channel in it unlike the N* which has the channel in the TB. I made a thin gasket to seal them up though.
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wow, that UIM is thin. Mine as well just weld the TB adapter fast lol.Comment
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