Stock throttle body size
Race Director
Joined: Oct 2004
Posts: 12,864
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Interesting...very interesting! My guess is that they are ALL 75mm. I had never heard of a 3mm increase for any year until I had this come up. And since the main engine change in C5 happened in 2001, it didn't make sense to me that the same TB part # would be used starting in 2000 (rather than '01) thru 2004.
In any case, a 3mm change probably wouldn't affect much anyway, but my guess is, any references to 78mm TBs are referring to an aftermarket piece, perhaps, or measurement from a different spot on the TB. Can you provide us the #'s that you see etched in the metal?
Thx,
Fred
In any case, a 3mm change probably wouldn't affect much anyway, but my guess is, any references to 78mm TBs are referring to an aftermarket piece, perhaps, or measurement from a different spot on the TB. Can you provide us the #'s that you see etched in the metal?
Thx,
Fred
Melting Slicks
Joined: Mar 2018
Posts: 2,502
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From: California
As it’s a tunnel or cone shaped understanding the actual measure is a bit more complex then just saying this is the inlet and outlet diameter...while one end is 78 the tail end is is maybe in the 49mm and u need to use a another tool to measure the distance of the cones internal width the divide by the number of measurements will give you it’s true size value ....
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Race Director
Joined: Oct 2004
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I apologize. Ive been up since 3 in the morning. You are correct. I do know which end is the TB outlet!! Somehow in my tired mind I had it in the front of the airbridge, like the MAF sensor is!!! Yes, the outlet of the TB bolts to the intake manifold. This will teach me not to post when I'm half asleep!!! Sheeeesh!!
Race Director
Joined: Oct 2004
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I also deleted 2 posts I made which were-OBVIOUSLY-Incorrect. I dont want to mislead people who don't know the correct info/terminology with incorrect info. WOW-I don't drink, either. But I might start now!!
Last edited by grinder11; Mar 16, 2021 at 08:11 AM.
Drifting
Joined: Nov 2005
Posts: 1,320
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From: NW Chicago
St. Jude Donor '12-'13-'14-'15
This is from a 2006 post on the forum that I found:
Stock TB on all C5s is 75 mm. You can only go to 80 mm with the LS1/LS6 intake manifolds. MAF is 75 mm for 97 - 2000, 85 mm 2001 - 2004.
A good improvement over stock is the Callaway 78 mm billet TB, (bell shaped inlet that improves flow, brass tb plate) and the MTI Racing composit MAF (97-2000 only, uses stock GM center section), gained 10 rwhp and 14 rwt on a h/c LS1, dyno test was done at MTI Racing, see March issue of Corvette Fever mag.
Stock TB on all C5s is 75 mm. You can only go to 80 mm with the LS1/LS6 intake manifolds. MAF is 75 mm for 97 - 2000, 85 mm 2001 - 2004.
A good improvement over stock is the Callaway 78 mm billet TB, (bell shaped inlet that improves flow, brass tb plate) and the MTI Racing composit MAF (97-2000 only, uses stock GM center section), gained 10 rwhp and 14 rwt on a h/c LS1, dyno test was done at MTI Racing, see March issue of Corvette Fever mag.
Cruising
Joined: Jan 2014
Posts: 11
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From: Augusta, GA
