2000 3100 TB

[jweir22]

I got this 2000 3100 throttle body off a buick century but i was disapointed to see it is still 52 mm,i thought they went to 56mm.

[v6h.o.]

no only the 3400's have 56mm's.

[Anonymous]

Other than the different sized TB, are there any other differences between the 3100 and 3400 intake?

[v6h.o.]

one says 3100 SFI the other 3400 SFI.

that is the only difference mainly. other than from one Body model using a specific EGR to another using a different one. those are the only differences in the plenums really.

i cant remember IF the newer 2000+ 3100 plenums have the same larger bore opening at the t/body or not. i wonder if they dont due to only having the 52mm t/b still. ? hmm something for me to measure next time i have one apart.

[jweir22]

I measured my 2000 3100 plenum and its 2.300" or around 58mm but still has a 52mm TB.The most i can bore the 52mm Stock TB is to 56mm just leaving enough wall so i don't break thru to the bearing opening.I am wondering on the stock 3.4 TB at 56mm already i wonder how much meat is on them i wonder if i could bore it to 60mm.I'll have to get one to try it.

[v6h.o.]

what i always do for throttle bodies is this, its hard to explain but here goes.

on most throttle bodies, you have a air bleed hole or a vacuum hole area for accesories. i know 3100's dont have vac ports, but im trying to remember if they have the same air bleeds (i should get off my lazy ass and go out to the shed to grab the 3 3100 t.b.'s i have dissasembled to one day get bored over)

where there is a small retangular air bleed there is a big large cavity behind there. this cavity to t/b bore thickness is usually only 2-3 mm thick. very skinny, what happens if you overbore is that you break through the cavity wall, (like in the case of the sides where the bearings are) to get around this on t.b's with vacuum port holes/air bleeds ect. is i take the spot that has the cavity, i take my drill and open up that cavity so its exposed through the t.body. this way i add some J.B.Weld to seal up that cavity.
i seal up that and any other area that will end up breaking through when overboring, or fill in those other areas that limit the overbore to go larger than you could originally do without breaking through castings..

once the JB.Weld has cured, then over bore it to whatever size is then permitable, and for the air bleeds or vacuum ports that you filled in, then take your trusty drill and using a small drill bit drill the bleed hole back into the casting, and use a larger bit to drill out the excess in the vacuum pipe fitting. ect ect..

i need to get pics of this, to show better what i mean.

what im trying to get across is this, you can go larger if you fix those problem areas where you will be breaking through the casting, if you can fill those area's with some JB and then once cured do the overbore, after that fix what needs to be done to make it workable again.
it is possible to go larger, you just have to do some prep work to make it so.

i get my t.b's bored out by a local guy and get a machine shop to make my plates.
either that or you scavange a larger t.b plate from something else that is of desired diameter.