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throttle body 85mm??

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Old 04-16-2010, 03:46 PM
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Default throttle body 85mm??

i bought this throttle body here at the parts area and the guy said its a 85mm
how do i determine if it is or it isnt the is a part number stamped on the side number is 23950
Old 04-16-2010, 03:58 PM
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the metric side of a ruler...
Old 04-16-2010, 04:02 PM
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so what is stock that is ported?
Old 04-16-2010, 04:03 PM
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stock is 75mm. ported would be slightly larger.

and an 85mm tb requires an adapter plate.
Old 04-16-2010, 04:06 PM
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well i have a stock one and i just bought a stocked ported one thinking it was an 85mm for $75
Old 04-16-2010, 04:16 PM
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ok so what do want to know? sounds like you need to discuss that with the guy you bought it from.
Old 04-16-2010, 04:17 PM
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i did he will re issue it to me once i ship it
Old 04-16-2010, 09:26 PM
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OK there is alot of misinformation in here right now. A stock tb is technically 75mm from factory as that is what the diameter of the throttle blade is. But there is a ridge in front of the blade that is 71.2mm so air is restricted through this ridge. By porting a stock tb and removing this ridge it makes it a true 75mm tb.

75mm is the largest a stock throttle body can be ported to, without adding weld to the outside, boring the throat and making a new throttle blade. So if you have a stock casting tb then it can only be 75mm.

Every gm ls1 98-02, 04 gto, 97-04 c5, ctsv 5.3, 4.8 and 6.0's are all 75mm tb's. Ls2, Ls3, Ls7 run 90mm from factory and thats it.

EDIT: And a correctly ported stock 75mm tb is the best route for any ls1, ls6 intake as they flow more than out of the box 80mm tb's that aren't ported and use a restrictor to get into the 78mm inlet of the intakes.
Old 04-17-2010, 01:00 AM
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gahhh mr. smarty pants
Old 06-23-2015, 10:14 AM
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Default 75mm throttle body

I have the same part number as well 75mm tb. If I plan to run a turbo set up with max 20 lbs what's a good throttle body to use. Maine a street show car but wanna turn it up when needed.
Old 06-23-2015, 11:30 AM
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Measure it lol



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