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throttle body porting

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  • Location:Orange County, California

Posted 04 January 2006 - 03:16 PM

I am looking for some one locally to port my throttle body( so. cal). I already got a quote from some one and they wanted too d**n much for just a ported throttle body. something like 289 for it and it was just a stock throttle body thats been ported. I know some people say its alot better to just get the stock one ported because you can squeeze more hp gains out of it than the aftermarket ones? can any one help me out? I have a 2002 chevy silverado 4.8l the mods that have been done so far are plugs, wires, intake, thermostat, i removed the chip and programer to get a custom pcm after i get all my mods done to it. Also who makes the best header for my truck? There are too many to chose from with claimes of 15+ hp gain? thanks David

#2 Haulin' 8.1

Haulin' 8.1


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Posted 14 January 2006 - 01:34 PM

David look into VR Racing's throttle body velocity stacks. Basically they make a plastic insert that streamlines the throttle body inlet. They claim it offers all the benefits of a ported throttle but for about $50 at summit. Based on looking at them and an educated guess I think it would work. I scored a BBK 80 MM Throttle body for my rig on Ebay for $100. That was a steal. The stocker was 78 MM but the inlet and outlet flanges are much smaller. I had to hog out the intake manifold's TB opening big time to remove overhang without using the reduceing spacer. So at some point their is a benefit to a larger aftermarket TB. No dyno tests or such but throttle responce and top end pull bumped SLIGHTLY on my stockish 496.


Edited by Haulin' 8.1, 14 January 2006 - 01:34 PM.

2001 Siverado HD 2500 SBCC in Black
GM Vortec 8100, Allison, 3.73, 4X4
Mods: Goodmark SS cowl hood, Ranch Hand bumpers, black toolbox, custom bed cover, full tint, Volant with home made ram air, BBK 80mm TB, Granetelli MAF, Marine Injectors, Hypertech, Champion RS12YC plugs, Magnaflow 3" dual in X-path dual out muffler and tail pipes, Fuzion XTi 265's, Velvet Rides, Pioneer 10" subs, amps, you know the usual stuff.
Coming soon: 4.56 gears, Autorotor supercharger by Whipple with Duramax intercooler, and GM HP3 cylinder heads.
If you've modded your 8.1's timing and run hard try Champion RS12YC plugs gapped at 0.055". Less knock, more power. Yes you have to change them more often (25K), but this is a performance mod. Besides they're cheap and easy to do.

Yea though I drive the the valley of the shadow of Diesel,
I will fear no turbo;
For your horsepower art with me;
Your bore and stroke, they comfort me.

#3 Butch 02 Denali

Butch 02 Denali


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Posted 15 January 2006 - 04:20 PM

Honestly David, the ported throttle body really isn't going to add any power to your 4.8. Did you know that the 4.8, 5.3, 6.0 and 8.1's all use the exact same size throttle body? Vernon saw very little gain even on his 8.1 and he went way up to an 80mm! Ported stock throttle bodies are about 75 MM, though they can be bored out to about 76MM they break thru the housing is numerous places and will need JB Weld patches. I've did one to 76MM on my 6.0, and it really wasn't worth all the time I put into it! Hardly noticeable difference. The stock TB on your 4.8 flows mush more air than that engine would ever need!
Butch 02 Sierra Denali
99 3500 w/350-4L80E
04 Avalanche 5.3
77 Vette, 408 SB blown and injected
2002 Pewter Sierra Denali DenaliTrucks
325HP 6.0 AWD with Quadrasteer
Wester's 91/93 Hot tune/Outlaw intake/Custom exhaust