70mm Or 75mm Throttle Body?

Paul Randle · Sep 28, 2012

i was wondering which one is best for mine car
here are a few things i have already installed
3:55 gears
bbk shorty headers with locking bolts
bbk off road h pipe into flowmasters
frpp alumunum driveshaft
bbk upper and lower intake spacers
Scott Drake Diff covers
Steeda subframes connectors
BBK shifter
FRPP clutch quadrant
FRPP smog pump delete
BBK LCAS/UCAs
FRPP blue spark plugs wires
MDS coil and cap
PA performance HO 3G alternator
Thank you

jrichker · Sep 28, 2012

Street driven cars need to keep the TB (Throttle Body) size down. The reason is there is a big change in airflow for a small change in throttle position. That makes the car jumpy and hard to drive smoothly in traffic without a lot of attention being paid to how much foot is on the accelerator pedal.

For your 302-308 cubic inch engine, a 65 MM TB is the best bet. The stock intake manifold is the restrictive part of the intake system, and putting a large TB on it won't get you enough HP gain to make it worthwhile.

The 70 MM TB is OK for an 302-331 cubic inch engine with high performance heads, intake manifold, cam and maybe pressurized induction.

The 75 MM TB is best for 342-427 cubic inch engine or a 331 with pressurized induction and high performance heads, intake manifold, cam.

madspeed · Sep 28, 2012

well said

RacEoHolic330 · Sep 28, 2012

+1. Match your TB to whatever size opening is on your intake manifold.

Paul Randle · Sep 28, 2012

cool thank you well i found on CL a 75mm throttle body brand new for $100.00 normally $200 so i had to jump on it. if i run a cold air intake to a 75mm throttle body and bore out my stock intake to 75mm would that be okay? is it possible that the motor will get to much air and cause i problem? in the near future i am planning on putting a cobra intake/ 24lb injectors and a high pressure fuel pump.

gearheadboy · Sep 28, 2012

88LX5.Oh · Sep 28, 2012

Why not do the Explorer intake swap instead of hogging out the factory intake?
Cheap and nice.

Or you could've spent that $100 on the Explorer intake in the first place and ran the stock TB. That would have gotten you farther than a stock intake with a 75 MM TB.

gearheadboy · Sep 28, 2012

Do you understand the words that are coming outta my mouth?

Paul Randle · Sep 28, 2012

I just bought this mustang and dont know much about parts but u have to learn somewhere so thought this website would be a good place. But i kinda wanted to replace the intake anyways. Say i went with a explorer intake wouldnt the intake have to match the tb? if so are you saying its better to get a explorer intake and just bore it out to fit the 75mm tb?

gearheadboy · Sep 28, 2012

Put the 75mm on the shelf till you get the proper intake to support it, or sell it. If you want to run an Explorer intake you can have it bored out by a machine shop to 70mm safely. More than that creates issues with the gasket sealing surface. I would think you should run a 70mm tops anyhow. Explorer or GT40 / Cobra intakes are good cost effective performance mod. Go to Ebay or the salvage yard and pick up an Explorer unit. Read up on the needed mods.

Paul Randle · Sep 28, 2012

Okay I am starting to understand. I don't need to install these part on my car now I would honestly rather get the proper intake to support the 75mm tb. Can u pleaser tell me the proper parts I will need to install to make it compatable with the 75mm tb? Thank you very much

sd331 · Sep 28, 2012

do a search on aftermarket intakes, with any intake u find you will probably still have to port the opening to 75mm. i dont know why people still say big throttle bodies will cause problems w/ driving, it doesnt, ive had 2 75mm tb on 2 cars and they both idled and drove like stock

gearheadboy · Sep 28, 2012

http://www.summitracing.com/parts/TFS-51500002/
That one will get you there. Its more money than the alternative listed above using a 70mm or 65mm unit. But to each his own.

88LX5.Oh · Sep 28, 2012

It seems to me you're wanting to build your whole top end off one small piece of the whole puzzle.
That's like building an engine around a certain cam. There's things you choose first, and there's things you choose last. You shouldn't be trying to match up parts to this 75 MM throttle body just because you got it so cheap.

What you need to do is figure out what your goals for the car are.
Is it just going to be a DD that's gonna see occasional strip use?
If so, I honestly would think no bigger than a 70 is needed.

I run a 70 and I've got aftermarket heads, cam, and intake so if that says anything...

Noobz347 · Sep 28, 2012

Paul Randle said:
cool thank you well i found on CL a 75mm throttle body brand new for $100.00 normally $200 so i had to jump on it. if i run a cold air intake to a 75mm throttle body and bore out my stock intake to 75mm would that be okay? is it possible that the motor will get to much air and cause i problem? in the near future i am planning on putting a cobra intake/ 24lb injectors and a high pressure fuel pump.

Who makes this 75mm throttle body anyway? There are only handful that are worth their weight in even Twinkies. Finding one on CL for $100 doesn't give me a warm fuzzy and is probably a piece that many here would pass on having known better.

Now if you tell me that it's a brand new Accufab then I'll get all excited about it for you. You tell me that you spent $100 on a 75mm from Professional Products and I'll snicker quietly as I head for the door to notify your next of kin. Ever been at or near 100 mph when the throttle body stuck?

One last thing... your report request is denied. These guys are doing their best to steer you in the right direction despite your fixation on this bargain basement part that you've located. If you ask for an opinion then you should weigh the value of that opinion... particularly from dudes who have been there and done that. This is not the forum to get positive feedback from, in order to back a poor plan.

RacEoHolic330 · Sep 28, 2012

I found my 75mm accufab on Corral for $130 with an egr spacer. I was pumped about that find!

Paul Randle · Sep 29, 2012

cool i understand guess it was just a bad buy lol btw its a BBK performance part bought right off the website. but i am just going to sell it and get a 70mm or 65mm on and get a cobra intake and just bore the intake out to fit whatever throttle body mm i have. At the end of the day i only drive the car once or twice a week i have a hybrid as a daily driver, but i would like to run 12's all natural thats the all time goal. where would be a good place to start? as in what are some good parts i will need and the order recommended to get them? also i would like to start off with cheaper parts then work into the more expensive ones.

Gearbanger 101 · Sep 29, 2012

Here's the issue. A 75mm T/B isn't worth while when you're breathing through a stock intake. Swapping out the stock intake really isn't going to net you much of an improvement without addressing the stock heads. Afer you get the heads and the intake upgraded, you really want to change out to something other than the stock cam to take advantage of the new capabilities. You see where I'm going with this....It's the snowball effect.

Ask yourself realistically....what have you got planned for your engine.

Most street builds won't benefit running anything more than a 70mm throttle body. Most intakes sold right now (save for a few) aren't even able to run a 75mm+ throttle body and spacer without serious porting...and even then unless the rest of the engine up to the task, that additional airflow isn't being utilized anyway. Your stock intake hasn't even got enough surface area to work with for that much throttle body.

Paul Randle · Sep 29, 2012

yeah i understand completely. well scratch the 75mm throttle. here is a list i put together tell u give me your recommendations Gearbanger101 and tell me if i am going in the right path? and also other parts that i may have skipped over. Overall i want to have a 12 sec car without the use of superchargers or turbos. i have a lot of bolt ons already but here are a few more i was thinking about doing.
CAI
70mm throttle body
cobra lower and upper intake
24lb injectors
high pressure fuel pump

Thats what i got some far and i am thinking that is a good order to get them in. Do you have any advice on my selection or if i missed anything? lastly what are some other things i can do to get to my 12 sec goal? sorry for seeming needy just wanting some help on my direction.
Thank you

Gearbanger 101 · Sep 29, 2012

IMO....if you want a solid 12-second car, you're going to need to address the heads and more importantly traction.

Skip the 24lb/hr injectors (the stock 19lb/hr injectors are good for over 300hp N/A) and fuel pump and spend the money you would have on them, on a set of junk yard GT40 or GT40P heads from an Explorer and some upgraded valve springs. While you’re at it, pick up the Explorer upper and lower intake as well. They're virtually identical to the Cobra intake and are about 1/3 the price. If you're on a budget, swap out the stock cam for an E303 (or if money allows, one of the many dual pattern grinds available out there) and you'll have yourself a healthy running 270-280hp 5.0L.

More importantly than all that...tires. Tires are what's going to make you, or break you here. Any of the major brand drag radials will work. Mickey Thomspon, BFGoodrich, Nitto, etc.

The above, combined with a "drive it like you stole it" demeanor will get you solidly into the 12's.

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