Different Throttle Bodies?

[6SENSE]

Ive got a couple spare Hotair TBs and noticed a difference between them. The air tube that goes to the IAC at the front of it is different sizes. One is quite a bit larger and sits lower and angled different. # on the this TB is 25519486. The other one is #25516152. I dont know if this is the only difference or if this even makes a difference. Maybe it makes a difference for idle quality?
Anyway, Im trying to send one out to Jay Jackson today and trying to decide which one. If anyone knows please let me know soon if possible, thanks.

P.S. maybe ones '84 and ones '85

[FJM568]

I think there were two different IAC's used...They may have different plugs on them...Use the TB that has the same size thread as the IAC that you use on your car...ie, make sure that the IAC that you use will plug in to your existing wiring harness...

[6SENSE]

Thanks Jim. With that thought, about the different IACs, it looks like the IAC housings are the same. So there should be no issue there. I could use either housing. As a matter of fact, I just tried screwing my IAC motor into each one and it went in fine.
Only question is, why the larger size tubes from the IAC into the TB air passage? (I noticed the tube behind the throttle plate on the turbo side of the TB is also larger).
I would naturally want to go with the one that would have better performance. Would more air to the IAC (with the larger tubes) give better idle, worse, or no difference? Why would they have changed?

[FJM568]

heheeh...why did GM design the hotair intake like they did??? Who knows!!! But damned if we ever figure out why they do anything like they do!!!

Back to your question...It may not matter too much which one you use...The ecm will adjust the IAC accordingly to whatever your motor needs at the time...

I will check later today on what number my 85's original TB has on it...Maybe GM noticed some type of problem with the 84's TB design and made some changes...Shouldn't hurt to ugrade to the later model TB...I will post later tonight which part number is on mine...

IAC will generally just affect idle...I don't think that it will affect WOT performance any...

[6SENSE]

Thank you
Im going to just guess that the one with the bigger tubes is the later model, since I have had one with smaller tubes on my '84(not that that means anything since I put this engine together with a number of extra parts to choose from ).
I'll go ahead and ship this one out to Jay, and find out for sure which ones which later on tonight. The more little things you find out about these cars, its something else. Interesting though.

[turbofish38]

Part #25516152 was used on the 84s and number 25519486 was on the 85s. They both used IAC #17079599.

[6SENSE]

Anyone know why they the change?