throttle body porting

URLIFEWASOC · January 4, 2006

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

Haulin' 8.1 · January 14, 2006

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.

Vernon

Butch 02 Denali · January 15, 2006

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!