3.4 Aftermarket TB Options

[bszopi]

I got an email the other day from a guy inquiring about aftermarket TBs for the 3.4 RWDs. Is there anything out there? I thought I remembered some people adapting LS1 TBs to fit the 3.4 plenum, but I'm not 100% on that. Just want to answer the guy's question and also be able to update the site with the info as well.

[StudlyCamaro]

not the LS1 TB its the LT1 TB that people use, it has the same hook ups for the IAC and TPS. im not going to get into why i dont think its a good idea unless you guys want to hear me go on and on about air velocity and area.. but i feel that adding an LT1 TB to a bolt on 3.4L is more harmful than helpful, however for a big camed car or FI car, hells yes its a great idea

its not a simple task, you have to chop the front of the plenum off, make an adapter for the TB so it can be integrated into the plenum and weld it all up.. dont forget the plenum is alumnium so welding it isnt exactly easy (it could be harder... but i personally hate welding alumnium)

or he could remove the front bar holding the butterfly in the TB, i forget what my friend calculated as far as useable area goes, but it was significant, but not too terribly much larger. if he does not feel confident in modifying the TB himself i can do it for him for 50$ if he sends me his stock TB back once he installs the modded one on his car

there is also a company based somewhere in canada if i recall correctly that makes a 62mm TB for the 3.4L f-body, i have the same thoughts on this TB as i do with the LT1 TB... but if i recall this one actually has a larger opening for the air, i'd have to do some math to make sure that is right


if he wants a plenum to chop up let him know i have one at my apartment that is for sale , shoot me an offer.


hope that helped

[XLR8ING]

By the "company in Canada", you likely mean us, but we postponed the 62mm RWD 3.4 TB because the neck just cuts back down again, so it's not really worth it. And we're not into selling 62mm TBs when 56-58mm is the max you're going to get behind it.
Design wise it'd be easy, because it's basically a mirror image to the 3.4 FWD model.
If someone wanted a bigger TB, the LT1 is what I'd suggest.

[2M6]

As far as using a larger TB in a Forced Induction setup, I wouldn't go bigger than the inlet pipes. Going larger than the inlet pipes can cause a low pressure area as the air enters the plenum. I am not sure how it would affect an NA engine though. I think you may see some gains if the engine has larger valves/cam(s).


I am not an engineer, these are just my opinions so take them as you will...

[Guest]

As far as using a larger TB in a Forced Induction setup, I wouldn't go bigger than the inlet pipes. Going larger than the inlet pipes can cause a low pressure area as the air enters the plenum. I am not sure how it would affect an NA engine though. I think you may see some gains if the engine has larger valves/cam(s).


I am not an engineer, these are just my opinions so take them as you will...

I agree, I even did a quick test of this at the track a few months ago, I had a 56mm TB on my truck and after a few things I noticed when driving on teh highway, I thought I'd test the theory of "less is more" and dropped my times by 2 tenths of a second, there may have been other factors, but I think this helped greatly, plus my tire slippage went up, basically inddeicating a return of bottom end torque, espesially when launching at just about 1500 RPM, when I had less trouble hooking up with the larger TB. I know not real conclusive, but it is an indication that sometimes, "less can be more".

[BMC]

3.4L (L32) throttle body

Its a good chance that the fellow that contacted you is one of my clients.

We install the GM 60 degree V6 into various cars including MG Bs as well as a current Triumph Spitfire. Kits for installation are around. I used to visit the old board alot, but have been so busy elsewhere that I have not had time here in a long time.

Anyway, there are several MG Bs out there with FWD and RWD engines, but to keep it simple, here is what we are currently dealing with-

1978 MG B. Lightened. Lowered, suspsension upgrades. gearbox is a T5 (yes, its only the V6 ratios in this one), 1998 Camaro rear axle narrowed to fit in this car with LSD and 3.42 ratio. An MG B is 1,000 pounds light then a Camaro to start with, has better handling and no power. Now it has more power then a Camaro, and better handling then a stock MG B (which has way better handling then a stock Camaro anyways)

Current engine specs:
Small camshaft upgrade, headers, better exhaust, better intake, upper intake plenum has been ported where the factory forgot to on every one of these(!), lightened flywheel, roller rockers (currently only 1.52 but might go to 1.6 if the new ECU allows) and upgrading to a Haltec (currently being fitted), bigger injectors and looking for someone to enlarge the TB.
Ohh, I almost forgot, it has Nitrous installed too.
In the future, a higher compression ratio, bigger cam or other items might be added as well.

The idea of installing a LT1 TB does not thrill me since underhood clearance is an issue, I want to make the improvement less expensive. In my opinion, too big of TB could be a bad idea. First, you will have saturated the amount of air that your engine can accept at, lets say 70% throttle opening. This will give the engine a false idea that it is not at full throttle. With the Haltec or other programmable PCM/ECUs, this can be overcome. Even though this can be overcome, it is not the easiest way of gaining power and overall is a bit much. A slight increase, say from 52mm to say the 58 or 62 mentioned above would be ok.

XLR8ING,
If you build the 58 and 62mm units, tell me about the 62. Is the intake manifold big enough to port out to 62/63mm? If not, what is the biggest you think it can be done safely? I have had to port out every manifold inlet just behind the TB due to casting in the way of the factory TB area, however, I never really looked to see how far we could port these out.


I have also done this same conversion to my 1982 Chevrolet S10. It has a 3.4L SFI motor and has successfully run without any problems for four years now. It is my daily summer driver, but I did drive it through last winter as well. It has a Camaro V6 ratio'ed T5 and with this engine/gearbox combo, it is one fast truck. When pulling my tendem axle trailer, it takes a little to get it off the line, but will pull a 2500 lbs car on the bed at 80 mph with plenty of throttle left... Just make sure the trailer brakes are working if you want to stop!!!!!!

If you know of a compnay who does TB borings on these, let me know, I could use a number of them if the power increase is worth it.

-Brian.

[StudlyCamaro]

jsut so you know a 62 mm single bore TB is larger than a stock LT1 TB

[BMC]

Hmm,
I thought the LT1 TB was a double 52 mm???

[v6h.o.]

i cant remember are the TPI and LT1 t/bodies 48mm or 52mm?

been a while since i played around with one...

which is it? anyone remember?

[RacerX11]

I know the stock TPI TB's are 48mm. I thought the LT1 TB's were a little bigger, which would make them 52mm. The double 48mm TB is bigger than a single 65mm (disregarding the area of the throttle shaft).

Marty

[StudlyCamaro]

I know the stock TPI TB's are 48mm. I thought the LT1 TB's were a little bigger, which would make them 52mm. The double 48mm TB is bigger than a single 65mm (disregarding the area of the throttle shaft).

Marty

the stock LT1 TB is also 48 mm , and you are right, i could have sworn that a stock LT1 TB had a smaller area than a 62 mm single bore TB, but the area of a 48mm dual bore TB is 1152pi mm^2 and a single bore 62mmtb is 961pi mm^2

i stand corrected