Stock TB inside the new larger TB


Side by Side

Ok...so you want a bigger throttle body. Well it’s your lucky day...GM has already been planning for you. Tools are simple and require maybe 1hr of your time. This mod has been done on a few cobalts and redlines already.

TB = Throttle body here after

Tools needed:
Dremel w/ bits for grinding aluminum
HPTuners
3.5" to 3" silicone coupler
Some T-bolt clamps (reuse your aftermarket intake ones)
A little creative thinking (for redlines its bolt and go with new coupler for cobalts a trip to home depot for a 3" PVC 90 is about it)

Parts needed"
Stock S/C
Stock S/C to TB bolts
New TB

New TB:
LS4 TB...offered on V8 fwd sedans from gm (impala ss and grand prix gxp), 4.2L DOHC I6 motor from trailblazer, envoy, etc. One from the 3.5L DOHC I5 in the H3, Colorado, canyon SHOULD be the same exact one but I'm not 100%

Ok so setup is real simple. On the backside of the TB there is a little lip on the top…dremel it off flat with the opening…just for more airflow…doesn’t hurt a thing



Disassembly:
Remove the stock TB and set the bolts aside...you need to reuse em. Note the location of the ports on TB and how they relate to the new and old TB…You need to install the new TB in the same direction.

Assembly:

***BEFORE YOU DREMEL…stuff a rag in the blower feed neck to prevent shaving from entering the blade area***

Remove the TB blade.

*the TB blade comes out easily using the 2 Torx headed bolts in the middle then rotate the blade and it’ll fall right out. Just remember how everything is oriented for reinstallation.

Place the new TB on in the same orientation as the old one…bolt it down using the stock bolts to make sure its in right place Use a sharpie and trace the outline of the opening onto the blower mouth. Should look something like this:



Ok…the reason why you are doing this is because the TB blade is too big to open fully against the stock S/C housing. So first you’re clearing room for the TB blade. But having the dremel in your possession allows you to port match and smooth everything out for even better flow then you’ll get from an adapter or just clearing the blade alone.

Reinstall the TB blade and keep checking clearance until the TB fully opens.

Ok now that it’s all nice and shiny. Clean it out and bolt the new TB on. Reinstall into car. Use you new coupler and mate it to your intake.

HPTuners Stuff:

To get it to idle right you only have to change 1 table in HPT…that’s it. See below picture for change



That’s it

Simple wasn’t it…Respect the MAD TYTE PAINT SKILLZ

Dan

 

Have done this myself with the help of the OP a few months ago and it works great. Other than the increase in airflow, there aren't any negative effects of using the larger TB as long as you edit the scalar value to the one he listed above.

Also...at WOT my air/fuel went nearly a point leaner so adjust accordingly.

 

did this a short while ago as well, works great.

 

Been wanting to do this, but lacking HPT access right now. Nice write up.

 

ok so what kind of gains are people seeing?

 

Like witt said we saw the AFR go 1 point leaner on the 1 car we did

thats a pretty significant difference in airflow

 

aweseome

 

subscribed

 

sweet lawnmower.........

 

we ported my throttle boday and noticed a gain, i can only imagine what this larger one will produce

 

LOL that my buddies lawn mower...I've had this TB thing done for 6 months now I just got around to posting it...

Here is some technical info on stock vs LS4 tb...if i told you where I got these files I'd have to kill you

Dan

Stock:


LS4:

 

Nice write up will save people some money without having to buy a adaptor plate

 

so, other than changing the scaler. nothing else needs to be done as far as the car acting retarded?

 

adjust MAF or PE for fuel and your straight.

i did this on my dummy blower for the turbo.

took it to work and had the whole blower intake runner machined out to match the larger TB.

 

hell, you fart wrong in the car, the maf freaks and changes.

cool, got ya

 

Thats what I would like to know...

x3

 

nice.... I have a 3" pipe for the intake adapter, should fit that no problem I hope.

 

i have a bunch of silicone adapters laying around from when i had a ls4 gxp car, now i just need the tb

 

Gains, anyone?

 

a full AFR point is a **** ton of air, thats what matters.

 

So would one from a 02 trailblazer with the 4.2 work?

 

COLORADO 04-05 Throttle Valve Assm; 3.5L
ENVOY 05 Throttle Valve Assm; 4.2L
TRAILBLAZER 03-05 Throttle Valve Assm; (4.2L)
HUMMER H3 06
BRAVADA 03-04 Throttle Valve Assm; (4.2L)
ENVOY XL 03-05 Throttle Valve Assm; 4.2L
ENVOY 03-04 Throttle Valve Assm; (4.2L)
IMPALA 06 Throttle Valve Assm; 5.3L
ISUZU ASCENDER 03-05 Throttle Valve Assm; 4.2L
GRAND PRIX 05-06 Throttle Valve Assm; 5.3L
ENVOY XUV 04-05 Throttle Valve Assm; 4.2L
TRAILBLAZER EXT 03-06 Throttle Valve Assm; 4.2L
CANYON 04-05 Throttle Valve Assm; 3.5L
MONTE CARLO 06 Throttle Valve Assm; 5.3L
TRAILBLAZER 06 Throttle Valve Assm; 4.2L
RAINIER 04-05 Throttle Valve Assm; 4.2L
SAAB 9-7X 05-06 6 cyl
__________________


list of throtte bodies that will bolt on.

 

i got mine off the LS4 Forums.

quite a few people have swapped to polished and ported units and/or even bigger(you can get one of those if you want to pay for it) so they sell there stockers for 75-100

 

this is awesome!

 

got my throttle body today....can't wait to get this set up