75mm TB on a 3.4 DOHC-too big?

[no_doz]

im looking around at the different common tb options that i will be presented with at local junkyards & there are a few that struck me as good choices, please let me know what you think.

80mm TB off of 96+ 5.7 camaros/firebirds
75mm TB off of 96+ stock 4.6 mustangs
70mm TB off of 88-83 stock 5.0 mustangs

i figure the 80mm is way too big & probably wont fit, & that the 75mm may be too big as well but i find that unlikely, although i figure the 70mm one is probably the best bet & will be the largest i can work with on 3" intake tubing (ill be making a home-made short ram intake to match & to put 8" between the TB opening & MAF sensor), but if i got 3.5" i could go as big as the 80mm IF it will fit in the stock tb mounting location.

until i can get the money for the M112 (thats right, ive found em for under 500 so im going that route), the tune, wideband, & etc... im going to just beef up the lq1 as much as i can on the relative cheap, & already have a set 4.0 jeep headers that i separated into the 2 headers (it was setup perfectly to make this very easy) & now just need flanged for the lq1 in order to bolt up.

for now i intend to go with the big TB, headers, short ram, & a WOT chip tuned to match, as well as possibly portmatching/mild porting all around depending on how much the intake gaskets will cost, & id like to shoot for 260 whp, do you guys think that with this setup & the proper tune-that this is a reasonable number?

[SofaKingWeToddDid]

maybe i didnt read something, but how do you plan on removing the OEM TB from the UIM?

[asylummotorsports]

maybe i didnt read something, but how do you plan on removing the OEM TB from the UIM?

By removing the bolts that hold it on? That would be the easiest way.

As to sizing, 70mm is likely too big for a N/A 3.4. In fact 65mm would be more than enough.

Get into boost and all that changes.

[bszopi]

Depending on the year, the TB is integrate to the manifold, hence the question about how it was removed...

Oh, and moved to the proper section.

[jmgtp]

I have a 75mm. Tip in is a bitch.

I use a 96 plenum and I welded up a big throttle tube that uses a 75mm Northstar TB on the end. I wouldn't recommend it unless you have other supporting mods and can deal with a touchy pedal down low. I'd also say 75mm is the absolute max you would want to go even on a really modded motor.

Asylum, keep in mind we're talking about the 3.4doch not the 3400. The dohc has a ~63mm TB in factory form so it can still benefit from something a lil larger that 65mm. I'd say 70mm is a really good compromise for controllable tip in and top end air flow.

[robertisaar]

already have a set 4.0 jeep headers that i separated into the 2 headers (it was setup perfectly to make this very easy) & now just need flanged for the lq1 in order to bolt up.

where the hell did you get this idea?

[no_doz]

i got the idea for the headers because i have a set of them laying around & they are setup like 2x 3 cylinder headers that come together into one pipe AFTER turning into 2 (not really sure why this was done on a striaght 6 engine, but it works out well for me). not sure how big the tubing is tho, ill measure & see if i can post a pic soon.

id rather do this than pay $300 to have someone make me up a set, especially since i went to UNOH & learned how to build & weld dirt track chassis with: mig, tig, stick, & oxyacetylene, as well as how to build & tig weld up headers (they didnt spend jack worth of time on mig & stick, but ive been mig welding for years so it wasnt really necessary).

attaching a different flange & hooking up the exhaust is the last of my concerns, it may be a pain like it usually is, but its not the most complicated thing to take care of if the headers are already built (they are shorty's).

[no_doz]

based on this ill be going with the 70mm off of the 5.0 mustangs, but i havent really taken a close look at my current TB because i didnt figure that it might be fixed to the intake! what year LQ1's had built in/fixed tb's?

[robertisaar]

everything 95 and under...

swapping to a 96-97 intake would be a good idea anyway, i believe they flowed better.

and assuming those 4.0 headers were correctly made, it might be a common thing to do since there is more support for the 4.0 straight 6 than there is for the LQ1...

[asylummotorsports]

Depending on the year, the TB is integrate to the manifold, hence the question about how it was removed...

Oh, and moved to the proper section.

OK Sorry! I did not know that.

[jmgtp]

Definetly go with the 96 plenum. That is what I did and like I said above I replaced the tb 'arm' with a custom built one which I made out of steel, prolly not the ideal material but steel is cheap and I can weld it, whereas aluminum I cannot. I'd try to find a GM TB of about the right size, why make things harder than they need to be when you can have the right TPS and IAC on there to begin with.

With all that you said above I think 260whp may be a stretch but I don't really know what headers will do.

[no_doz]

same here-im hoping the headers & tune will make a big difference, i guess ill just hold off on a bigger tb for now, because i didnt realize the stocker is 63 & that its part of the manifold! i wouldve never guessed...

but then again i have that gtp out in the garage & i like havent touched it, i want the motor out of it now, & considering my gf's aunt made the chassis crap by replacing the odo with one that had 5-10k miles more mileage, & instead choosing to put an odo discrepancy on it rather than to eat the extra mileage (ugh), & with an auto trans i just see no appeal in the grand prix body.

[SofaKingWeToddDid]

i was just under my hood all weekend, thats how i know. but i know you can machine the inside diameter of the integrated TB if you know a good machinist.

[SofaKingWeToddDid]

i only know cuz i pulled my UIM apart to send it off to powder coating. had to take the TB apart otherwise it would have caused some problems being heated up for powder coating

[SofaKingWeToddDid]

sorry for the double explanation, im having browser problems... crappy ass old computers.