Thread: TB porting questions..

what year cars do i need to get a n* tb from to work on my 99gtp

Originally Posted by 99GPGTP

what year cars do i need to get a n* tb from to work on my 99gtp

2000+ are the ones you should try for

U guys are cool I was bored & all video gamed out & was lookin for somethin' to do. I google searched "How to port a throttle body on a Grand Prix" & it led me back to this site which I actually visit ALL the time During the process of porting my throttle body similar to the end result in Reptile's pic I came into the house on 1 of my MANY breaks ;D I went on ZZP.com & they sell similar ported throttle bodies for I think $350. I dunno there was like a Stage 1 & a 2, whatever. I was too busy laughing & I had lost interest by then. After I finally finished & put everything back together I took the Beast for a ride. The throttle response IS a lot better. Seems that most my drivability symptoms went away during the ride. Perhaps the engine was starved for air & making the opening able to suck in roughly 20-25% more air helped out a bit. Swapped the TPS (Had a spare throttle body with sensors intact from an engine swap in Oct). Perhaps it was that or maybe the cold night air responded better. Custom tune coming SOON. I would definitely recommend this as it's for sure the best of the free mods along with possibly porting ur SC however u can port that sh*t all u want the air has to enter from somewhere & if it's creating a stupid bottleneck effect then it won't matter. Open that sh*t up!!!

Sweet.

Really isn't nothing to be afraid of...




This is the almost completed result (test fitted sensor), just be patient.

Take down big chunks at first if you can, I used a drill press, lol, to take a majority of the material off. Then went slow as you near the end. A bench vise to hold the TB works well for the grinding. I also used a bit extension, with a small piece of EMT electrical tubing (1/2") as a sleeve to hold the bit extension loosely and allow it to rotate while grinding and apply pressure easily.

Don't worry, as Reptile mentioned, you will bore holes through the casing on the TB. Just rebuild it back up, I used the JB Weld Stick which is easy stuff to use. It's rated for 500*F so no worries there too. Make sure the surface you're putting the JB weld onto is all cleaned up nicely though, just as a precaution.

You cut off a chuck of the stick and roll the bead between your fingers. Then with a little water while mixing it up (just wet fingers and continue to mix it between fingers) and this made it real pliable and allowed easy shaping. It will set up fast as time elapses but no worries, there's plenty of time to work the material, say 5-10 mins. Allow it to dry for a while but not all the way, say about an hour, then I took some material off again as the JB weld is not fully set and easy to remove, but left it high enough to final grind/sand. Be careful here as it's easy to take too much off and you'll have to re-mix and apply the JB weld again.

Then the final grind and sanding was accomplished with a dremel using the flexible extension.

Added bonus... Paint job! lol...

Very nice! Has anyone flow tested one of these against a stocker?

Hmm, all I have now is a stocker that is mildly ported. Can I hog it out and install a diff throttle blade (what size) or run a northstar or LS1. I could make the larger throttle blade if there is enough room to open the TB throat. Made an adapter once for another member on here to run an LS1 TB and I have the pattern still.

thing about swapping blades is you need to be 100% round in matching the new blade. if not you will be letting air by. if it lets too much by the you wont be able to idle correctly as with the IAC completely shut you still will be getting air passing.

on my DOHC i spend lots of time porting it. went thru 3 diff stages of porting on it. 1st was just rounding the entrance lip. 2nd was feathering the rounded edge all the way back to the blade and port matching the exit. 3rd was making an inverted bell shape inside the inlet of the TB and then removing one half of the bar that holds the TB blade. allowing more cross sectional area at WOT and removing the extra threads from the screws. the DIA of the DOHC's tb is 64mm but with the extra area i calculated it would be equal to a 71mm if the blade bars were left intact.


one idea i would like to try is this.... i am currently running the maf off my DOHC as i bored it out to 3" and has very little restriciton. what if we cut the first half of the L67 TB off and take half the housing of the MAF and mount and mold it to fit the TB. this will solve the issue i have with the TB being like 80 feet long!! my DOHC's TB was less then half the size of the 3800 tb's.

my $.02 on the northstar's are they dont have a good shape to them. i would rather have a slightly smaller TB blade but have a smoother transition to increase velocity then have a bigger blade that doesnt have a good flow to the blade.

whats the diff... north star is 75mm and stock l67 is 69mm? lets find out...

Area of northstar= Pi r^2= Pi (75/2)^2= 4418mm^2 factor in some sig fig's and we have an aproximate area of 4400mm^2
Area of L67 TB = Pi r^2= Pi (69/2)^2= 3739mm^2 factor in some sig fig's and we have an aproximate area of 3700mm^2
Area if we remove 1/2 TB bar = 3*69= 207mm^2 factor in some sig fig's and we have an aproximate area of 200mm^2

so a north star has an area of 4400mm^2 and if we remove 1/2 the TB bar it will be 3900mm^2
basicly the N* has 11% more cross sectional area then if the l67's blade was removed... now does that 11% make up for the loss in velocity due to the shape? i dont see a port job on a TB making 10% more power, but 10-11% more flow?? when porting my DOHC tb i remember seeing close to if not more then 10% increase in MAF numbers. unrealated to this the boring out of the maf caused a 35% change in the maf table.