75 mm throttle body on stock plenum

Adam Vinnicombe · Dec 17, 2019

Hi all I've just been given a 75mm throttle body for free but before I go out side in the rain and take my stock one of can you lot answer this question
Will a 75mm throttle body fit on a stock 2001 ford mustang plenum?

07GtS197 · Dec 17, 2019

Yes but its much bigger than the stock plenum. I would get a new plenum first and install both at the same time.

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96blak54 · Dec 17, 2019

Itll bolt on directly, but their may need to be some trimming on the entry id hole of the plenum for clearance of the throttle blade.

07GtS197 has it right...just buy an aftermarket plenum.

Truth be told the mustang plenum was the worst. If their can be a worst when using stock part, its the mustang. The crown victoria/ towncars got the better flowing plenum, but it looks ugy

Adam Vinnicombe · Dec 18, 2019

Thanks for your replys
So I've been doing some reading and it's a bloody minefield out there on what size and what make plenum to go for. I was going to go with the Accufab 75mm plenum to match the 75mm throttle body but it's a 50/50 split out there between the 70 & 75mm set up. Has anyone here ever used either of these?
Here's a quick list of all my engine mods
Diabolospot 93 octane tune
CAI
Mac Long tube headers
4.10 gear
Pro chamber mac flow exhaust system
No Cat's
SVT fuel pump
Fms alloy prop shaft
Looking into stage one or stage two cams now not sure which way to go on these or I may keep the stock cams and fit a supercharger

ttocs · Dec 18, 2019

I know that everyone with the 5.0 loves to put the 75mm and then say they felt a difference but I know the throat for the gt/cobra intake is only 70mm so I think their butt dynos need to be calibrated.

07GtS197 · Dec 18, 2019

Its been a long held belief in the 2v world that a 75mm tb is too big for an na car. While I’m sure it doesn’t help much more than a 70mm but we’re talking a few hp at most, I don’t believe that the extra 5mm will cause low end torque loss. I would run what you have. I have a 75 mm tb with a c&l plenum. Coming from stock I could feel a difference.

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96blak54 · Dec 18, 2019

Im not going to admit this very often, so you, the reader, consider yourself lucky to have witnessed this!

ttocs is right

Buying a plunem to support the 75mm opening needed for the 75mm throttle body is all still being fed into the stock manifold.

So as to which plenum is better?....it doesnt matter. Just go with the one you like.

ttocs · Dec 18, 2019

sometimes I am a perty fart smeller!

Adam Vinnicombe · Dec 18, 2019

OK so is there a better manifold to fit so the 75mm throttle body and plenum can work better?

96blak54 · Dec 18, 2019

Yes actually their is, but only 2 can be purchased new.

Edelbrock and pro power products.

07GtS197 · Dec 18, 2019

But blak will either of them really gain you anything with just bolt ons? Back when the 2v was still big this used to be a huge topic and the concensus was that it wasn’t worth it. However I have have yet to see back to back dyno or track runs to back up whether it’ll gain anything or not.

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96blak54 · Dec 18, 2019

07GtS197 you nailed it. Spend $3000 in bolt ons to gain 20rwhp is the typical 4.6l enthusiast. And we all did it too!

Are the bolt on not worth it, one might ask?

No ...not really. The hp gain to money spent isnt worth it to a stock unopened engine.

That same coin spent on a forced induction system would easily gain 100rwhp and retain all the stock components.

And knowing what we know today.....pull the engine, swap to coyote rods, forged pistons, and install the supercharger kit and your good to 700rwhp.

Unless you plain out dumb like me and clinging to the modular platform. I still believe 400rwhp can be achieved reliably from on of these things naturally aspirated.......

OLD H2S · Dec 18, 2019

When I switched to the Edelbrock with a 75mm TB I gained 10 RWHP but I lost 15 RWT.
I am running a 72mm TB with the plastic Pi manifold.

07GtS197 · Dec 18, 2019

The biggest limiting factor are the heads. If they flowed like the 4v heads and had an intake to support it a 2v would have some pretty good potential. Then throw in vct and youll have a nice powerband too.

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d.garza18 · Dec 18, 2019

96blak54 said:
07GtS197 you nailed it. Spend $3000 in bolt ons to gain 20rwhp is the typical 4.6l enthusiast. And we all did it too!

Are the bolt on not worth it, one might ask?

No ...not really. The hp gain to money spent isnt worth it to a stock unopened engine.

That same coin spent on a forced induction system would easily gain 100rwhp and retain all the stock components.

And knowing what we know today.....pull the engine, swap to coyote rods, forged pistons, and install the supercharger kit and your good to 700rwhp.

Unless you plain out dumb like me and clinging to the modular platform. I still believe 400rwhp can be achieved reliably from on of these things naturally aspirated.......

One day you’ll figure it out my man

OLD H2S · Dec 19, 2019

Thats called a 2005 3V engine.

Adam Vinnicombe · Dec 20, 2019

And how expensive will it be to buy and fit and tune a 3v in my 2001 ford mustang GT?

Chip66 · Dec 20, 2019

The butt dyno often lies to you because it is attached to your right foot.

The bigger throttle body really only does anything if it was the biggest restriction in the first place.

The reason so many swear by them is that the larger TB can dramatically increase throttle response. With the same throttle angle on the low end, they let more air through than a smaller TB. However, when wide-open where it counts, the smaller TB is no longer the restriction in the system and will perform the same.

If you think I'm wrong about this show me a dyno difference with only at TB change.