lt-1 throttle body on a 3400?

[stormwolf1972]

has anyone ever modified a 3400 upper intake to accept a lt-1 throttle body?.....i am swapping the top end off a 3400 onto my 3.4 firebird and want to upgrade the tb while i am at it....any help?and you guys have been more helpful then most of the guys on the RWD forums...they mostly say swap in a v8...lol...you actually try to help me and i thank you for it

[treeZ24]

not sure on the size of the outlet on the lt1 tb, but it is a dual 48mm isnt it? which is pretty big.

the largest a 3400 intake neck on the plenum will go is a 65mm iirc.

[stormwolf1972]

i have been looking at an edelbrock dual 53 mm

[RacerX11]

Dual 53mm is HUGE for this engine. It will be tricky to adapt a dual-TB unit to the 3400 upper plenum. You are better off with a large single.

[El_Diablo]

heh, good luck... you would have to make a whole new neck, might aswell just build a sheet metal plenum with air horns and all...

[stormwolf1972]

i have a friend that can weld aluminum...he does it for a living....if i can get a tb he can machine an adapter plate and weld it to the neck of the plenum.....the lt-1 tb are sold for the 3.4 rwd with modificataions to the plenum...i am doing a top end swap off a 2000 3400 onto my 3.4 firebird and a bigger throttle body will help me hit or exceed my goal of 200 to 230 rwhp

[RacerX11]

I am familiar with the LT1 TB's mounted on modded 3.4 upper intakes. The shape of the 3.4 intake makes this a lot easier. Not saying it will be impossible, but like I said, it will be tricky. The fuel rail and FPR are right where the TB will want to be.

Your welding and fabricating resources are better off adapting a large single TB for your goal. A 65mm-70mm single should be capable of supporting 220-230 whp, assuming the rest of the engine is up to the task.

The dual 53mm is pretty close in size to a single 75mm, which comes stock on LS1's, and supports well over 300whp worth of air flow. Don't waste your time trying to fit a square peg into a round hole when it doesn't gain you anything.

[ryan.hess]

I've got new 75mm throttle bodies in the mall... might be buried on page 3 or something...

Probably too much for a stock 3400. I wouldn't say 300WHP, but 300 flywheel hp. They are used on 4.0's, which have 250 flywheel hp. If you're planning on modding to that power level, it's something to look into.

[bszopi]

Was waiting for Ryan to pop in with one of his TB's...

[stormwolf1972]

so i should just use a single large tb from an lt-1 or ls-1?....and i am mounting this on a 3400 upper intake not the stupid y shaped piece of junk that came on the car...it will be headed to a scrap yard very soon

[RacerX11]

so i should just use a single large tb from an lt-1 or ls-1?....and i am mounting this on a 3400 upper intake not the stupid y shaped piece of junk that came on the car...it will be headed to a scrap yard very soon

Yeah...we got that part...you are doing a 3400 top end swap..told us several times already. Take a good look at the 3400 plenum, and you will see why a large single is best. One of Ryan's is probably your best option.

I wouldn't scrap the stock 3.4 intake. It is an improvement over the earlier gen1 MPFI intakes, so you might try listing it for sale on here or the Fiero forums.

[RacerX11]

I wouldn't say 300WHP, but 300 flywheel hp.

The stock LS1's put down 300+ whp on 75mm TB's, so it is possible.

[sharkey]

http://www.megamanual.com/v22manual/minj.htm#throttle scroll down a bit and you will see the tb size calculator. it gives you an idea on how big you need to go. keep in mind that to big causes tuning issues (makes it harder) and makes the throttle touchy

[ryan.hess]

so i should just use a single large tb from an lt-1 or ls-1?....and i am mounting this on a 3400 upper intake not the stupid y shaped piece of junk that came on the car...it will be headed to a scrap yard very soon

Remember too that LT1's and LS1's are RWD longitudinal, which means the throttle cam is pulled from the back.

To make it an easy swap you want a throttle body from a FWD car that's pull from the front.

Edit- in the firebird you'll need an LS1 throttle body. I thought this was in a FWD car

[SappySE107]

I have someone else that wants this done (dual throttle plate). It does have its advantages for having more possible airflow at WOT but still having less air at part throttle than a single larger plate. Drivability should be easier.

Doing it is not easier though. To use an LS1 tb on a 3400, you will need to cut and weld a new flange anyway, or adapter it to stick out more and do a lot of porting. Id rather cut and weld.