65mm-70mm tb

mace6 · Dec 12, 2004

What size TB should I use? Installing Tw heads, street intake and stage 1 cam on 94 GT vert. I've been told both 65 and 70.

jimmy

urban96 · Dec 12, 2004

70 or even a 75 wouldnt hurt

Black95GTS · Dec 12, 2004

Your street heat manifold is already setup to accept a 75mm TB... I would go with that. The extra size will not hurt you, and as you continue to build up your car will only enhance the affects of other mods.

wytstang · Dec 12, 2004

Which ever one you find the cheapest either one will work about the same.

Grn92LX · Dec 12, 2004

75mm. Are you converting to fox style or keeping it sn95 style? Reason I ask is because if your going fox style use an accufab, but if your keeping it sn95 I dont know what brand to recommend since accufab doesn't make TB's for your years. I had an accufab 65mm then switch to an accufab 75mm.

ProKiller · Dec 12, 2004

i would either go with a 70 or 75. your setup can take both and work well. i would go with a 75. it will allow you to grow with your setup.

Joes95GT · Dec 12, 2004

.....

Joe

mace6 · Dec 12, 2004

I'm going to stay with the sn95 for now so I guess the 75mm is my best bet., also, will i need a custom chip? one person told me that on 94-95's that the cam would lower the vaccume pressure and that my computer would have issues with that. thanks for the help!!!!

5spd GT · Dec 12, 2004

Go no bigger than 70mm with that setup...

Good Luck with it...

Grn92LX · Dec 12, 2004

Joes95GT said:
.....

Joe

Good answer , Joe I know you wanna say it too, but you know whats gonna happen....

greenlantern · Dec 12, 2004

IMO 75mm is too big. Bigger is not always better. Remmember that what your after here is velocity. 70mm is as big as you will ever need on the street. I've seen several tests done at the dyno shop where 65 was swapped for a 70mm and there was literally no difference in performance, so in this instance get the whichever one you get the best deal on.

Joes95GT · Dec 12, 2004

greenlantern said:
Bigger is not always better. Remmember that what your after here is velocity.

Is it now?

This is fuel injection. Not carburation. Velocity is "made" in the runners of the manifold, not the throttle body.

mace6 said:
I'm going to stay with the sn95 for now so I guess the 75mm is my best bet., also, will i need a custom chip? one person told me that on 94-95's that the cam would lower the vaccume pressure and that my computer would have issues with that. thanks for the help!!!!

With most camshafts, you will lose an inch or so of vacuum at idle. No big deal. My car lost about 2 inches at idle, and it still runs fine. Unless you are putting a Pro-stock-like cam in the car, you'll be fine and vacuum loss will not be an issue.

Joe

5spd GT · Dec 12, 2004

greenlantern said:
IMO 75mm is too big. Bigger is not always better.

My thoughts exactly...

A TB can almost be used as a tool for velocity...and what if the runners are to "big"...what velocity is made then...many different factors come into play...not one specific part...

A 75mm would be more ideal for a stroked or blown car...

By swapping just TB's on a h/c/i engine...you would lose some torque (low rpm throttle response) on the lower end of the rpm spectrum...at WOT...

65 or 70mm would be fine for YOUR application...

mackey · Dec 12, 2004

I have the same intake you have and I am going with a 75mm throttlebody.

ARed1995GT · Dec 12, 2004

Grn92LX said:
75mm. Are you converting to fox style or keeping it sn95 style? Reason I ask is because if your going fox style use an accufab, but if your keeping it sn95 I dont know what brand to recommend since accufab doesn't make TB's for your years. I had an accufab 65mm then switch to an accufab 75mm.

everytime i see a throttle body thread i check it and see what u have to say haha, whether its on here or corral.. ur always repping that 75mm tb, what would u suggest for my car?

Joes95GT · Dec 12, 2004

Lets think about this a little bit...

I contend that velocity is created in the runners of the (long) runner intake manifold. Others contend that throttle bodies regulate velocity. If that was the case, then could you use a 60mm TB on a Vic. Jr. intake manifold on stock heads and it would run OK because the TB is creating the velocity?

Joe

Grn92LX · Dec 12, 2004

ARed1995GT said:
everytime i see a throttle body thread i check it and see what u have to say haha, whether its on here or corral.. ur always repping that 75mm tb, what would u suggest for my car?

70mm if you really wanted to change it. I'd save up for some heads/cam and do it all at once personally.

Go get 'em Joe. I'm glad I have other smart guys backing me up on this topic

5spd GT · Dec 12, 2004

Joes95GT said:
Lets think about this a little bit...

I contend that velocity is created in the runners of the (long) runner intake manifold. Others contend that throttle bodies regulate velocity. If that was the case, then could you use a 60mm TB on a Vic. Jr. intake manifold on stock heads and it would run OK because the TB is creating the velocity?

Joe

I was referring to HIS application...not a bottleneck (stock)...which actually flows fairly decently for stock...You can give or take the "velocity" theory...you just can't be GENERAL with a TB statement...

I never said the TB is the only way to regulate velocity...it is one of many engine components you can use...

And to the original poster...make sure you have a nice flowing MAF/calibrated for you injectors (24 or 30lbers)...

Mike - I enjoy being inferred as "stupid"

"Some" people make their analysis of what part to get by trying to be different than others...but "if it ain't broke...don't fix it"...their are simply just some personalities that like to go different and praise it without having any real back-up on either side...

Some people need to give suggestions for a particular setup and not so GENERAL...

David

greenlantern · Dec 12, 2004

Agreed 5spd GT.

Installing too large a throttle body can hurt performance, particularly torque as will installing too large a carburetor. This is especially true when talking about natually aspirated cars. Turbocharged or supercharged cars make up for the torque loss by capitalizing on high rpm airflow. The last thing to remember about choosing a throttlebody is shouldn't be larger than your mass air meter. You want to create a funnel for the air, so the mass air meter and filter should be large and necking down to the throttlebody.

Grn92LX · Dec 12, 2004

David, I was NOT calling you stupid. I wouldnt do that.

The last thing to remember about choosing a throttlebody is shouldn't be larger than your mass air meter. You want to create a funnel for the air, so the mass air meter and filter should be large and necking down to the throttlebody.

Wrong in oh so many ways

65mm-70mm tb

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