3500 plenum and 70mm throttle body

[MidnightriderZ24]

i dont post much on here, but i figured i should post this. i wrecked my 3400 plenum being careless when bolting it down and ended up cracking the mounting ends off, and so i just jb welded it for the time being, and i started to look for a 3500 UIM. i got one pretty cheap and picked up a 1998 4.3 vortec tb dirt cheap and started to think of ways to mate them together and this is what i came up with. excuse the sloppy vacuum lines... i dont have any pix of the UIM finished porting either... the top end difference it made is amazing! it really compliments my headers and porting.

[StudlyCamaro]

RE: 3500 plenum and 70mm throttle body

that looks great!

[SappySE107]

RE: 3500 plenum and 70mm throttle body

Does that throttlebody just bolt up with the adapter and thats it? If so, ill keep my plans for the 3100/3400 throttlebodies and work on an adapter like that to use the larger TB. Hows the low end?

[MidnightriderZ24]

actually the low end feels better..... everything improved. deffinately top end around 5000 rpm. yes with the plate the throttle body will just bolt on. i might be making a few extra since there is some interest.

[project60degree]

what is the plenum off of? and is thet the stock size of the 4.3 tb?

[MidnightriderZ24]

the plenum is from a 2005 pontiac G6, and the throttle body is from a 1998 s10 blazer with a 4.3 vortec, and i removed the air baffel on the butterfly and tig'd the holes shut, and just polished up the inside of the throttle body, IMO it was 100% worth it, just look on car-parts.com and u can pick the tb's up for cheap, i picked mine up right in town for $20, and the 3500 plenum i got off car-parts.com too for $80 new! :P

[project60degree]

hows overall performance gains? the UIM bolts right up to the LIM?

[Kohburn]

hey if they swap then that means people could swap the better looking 3400 intake onto the 3500

[Berettaspeed]

TQ wrench is your friend

[v6h.o.]

actually the low end feels better..... everything improved. deffinately top end around 5000 rpm.

I noticed the same thing when I put my 3500 plenum on last year. 5000+ rpm was a noticable powerband gain.

Looks good.

[onefastV6]

That looks great. What all did you have to do to get it to bolt up?

All I would have to do is get a 4.3L TB, 3500 plenum, make an adapter plate and bolt it on?

Your throttle cable bracket was that modified or was it custom made? Also would I have any problem hooking up cruise control?

[MidnightriderZ24]

the throttle cable bracket was modified a little. as for cruise i removed it so it would take some more things to get that to work. to only modification i had to do was die grind the IAC hole behind the butterfly, but ill get pix after im done painting it so people know what im talking about

[mcgavinz26]

Wow, nice looking work. So how much does the 3500 intake taper down from the throttle body's 70mm diameter? That thing doesn't have a 70mm or bigger opening from throttle body to the plenum cavity does it? Either way, thumbs up.

[v6h.o.]

Stock the 3500 plenum, has about a 66mm or so throttle opening IIRC, been a while since I measured mine.

It necks down a slight bit but not much.