What size TB?

[Fast95Stang]

I was thinking about putting a throttle body on my car this spring but wasn't sure what size. Right now it has a stock intake but I will be rebuilding my engine next winter. After it's rebuilt it will have a Trickflow intake w/ Trickflow intake adapter for 94-95 Mustangs. (I'm planning on building a 306) The inner diameter on the adapter is 75mm. Since that is 75mm I was thinking of just getting a 75mm tb. Is it possible to have a tb that is too big? Will a 75mm tb fit on a stock intake?

Thanks in advance to all who answer. :thumbs_up

[Nick 1]

Is it possible to have a tb that is too big? Will a 75mm tb fit on a stock intake?

Thanks in advance to all who answer. :thumbs_up

Yes

Not sure

65mm Tb would work nicely in your application. :thumbs_up

[Greg@GLD]

IMHO, 75 would be overkill, 70 would be about right, room to grow and it won't cost low end either.... 65's are kind of standard fare for the moderately modded combo.

[FastGT94]

For H/C/I a lot of the builders are recommending 75 but with stock heads, I'd say stay 65 or 70 max.

[Twirkin50]

Go big or go home....

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7954702398&category=33558&sspagename=WDVW


Thats just not right! :eek:

[93GT]

I would say match the tb to the opening at 75mm. I have had a 75mm throttle body for a long time. Any time you go from a small opening to a larger or large to small abruptly you disrupt the flow of the air.

[Greg@GLD]

I would say match the tb to the opening at 75mm. I have had a 75mm throttle body for a long time. Any time you go from a small opening to a larger or large to small abruptly you disrupt the flow of the air.


That's a good point Mike. If the adapter is larger and the opening on the intake is smaller, then you will have a lot of turbulance created by smaller opening. It won't hurt going the other way- If the opening on the intake is larger than the TB, there won't be any turbulance created.

[93GT]

That's a good point Mike. If the adapter is larger and the opening on the intake is smaller, then you will have a lot of turbulance created by smaller opening. It won't hurt going the other way- If the opening on the intake is larger than the TB, there won't be any turbulance created.According to some of the air flow experts, going from a smaller diameter to a greater one with an angle greater than 15deg can cause disruption of the air streams boundry layer increasing drag.
:D So technically there would be some turbulance. Whether it makes a big difference in the real world I probabably doubt it. Both my Edelbrock intakes were only 70mm opening, so I just had to grind a little out to match.

[Fast95Stang]

When I rebuild my engine I am going to use the Trickflow H/C/I package from Summit. I am going to get the street intake, not the track heat. I do not know the size of the opening on the intake but if needed, I could grind some out. Since I'll be replacing the head and cam as well, should I go with a 75mm tb?

Thanks for all the advice.

[Greg@GLD]

According to some of the air flow experts, going from a smaller diameter to a greater one with an angle greater than 15deg can cause disruption of the air streams boundry layer increasing drag.
:D So technically there would be some turbulance. Whether it makes a big difference in the real world I probabably doubt it. Both my Edelbrock intakes were only 70mm opening, so I just had to grind a little out to match.

Well, then technically, the stock TB causes a flow disruption.. :D
The blade of the TB and the screws in the shaft could also factor in, at what point is it critical. I think your original point was very valid, it's not a good thing to run into a "ledge".

[93GT]

Well, then technically, the stock TB causes a flow disruption.. :D
The blade of the TB and the screws in the shaft could also factor in, at what point is it critical. I think your original point was very valid, it's not a good thing to run into a "ledge".
It all adds up. :D j/k
Fast95Stang-Any of the bigger throttle bodys should work about the same. I think the reason people don't like 75mm is that they will let quite a bit more air in at the same tps voltage than a stock tb or smaller. Maybe that has some effect on the power? Otherwise I can't see how anyone could lose torque from too big a tb. It's not a carb. I had a 4" powerpipe on my car. You would think that really would have killed the torque if a bigger inlet was bad. :p I believe it's just another internet myth. :D The 70mm should be more than enough though.

[Fast95Stang]

Just looked on the Trickflow website and the opening to the intake is 75mm. Since that is 75mm wouldn't it be the best to keep it 75mm all the way from the tb to the intake?


This is off the subject but, I just ordered a UPR Blue Thunder short throw shifter. :banana: The price is right- $100 I also got a coupon code from UPR so it was actually $95 :rockon:

[93GT]

Just looked on the Trickflow website and the opening to the intake is 75mm. Since that is 75mm wouldn't it be the best to keep it 75mm all the way from the tb to the intake?
\:I would, but I'm sure a lot of guys will tell you it's too big. Go with the 70 or 75 whichever you can find cheaper.
:flg: As long as it's not a restriction, I don't think it's all that important. Even with boost, there are guys making lots of power with the stock tb.

[93GT]

Some people claim to lose throttle response with the 75, but, FWIW, I was gonna run a 75mm with an 80mm MAF before I went carb.I would think you gain throttle response.
:D You only have to push the throttle a little bit to let a lot of air in. :rockon: :D The 80mm Pro-M worked great in my car and was an improvement over the 75mm bullet I think because of the way it samples the air. But now I'm back to a bullet again.

[Fast95Stang]

I suppose I'll go with the 75mm. That sounds like it will work out the best. Thanks for all the info!