This has been a touchy subject around herelately and I know thateveryone has their own ideas butI found this article aboutwhat size throttleAccufab thinks you need. It's pretty interesting. By this chart my 65mm I have nowis all I need for my 331 but I amwanting to get a 75mm throttle body to see what will happen.

http://www.accufabracing.com/article%203.htm

 

good find. it was also posted here also on this debate

https://mustangforums.com/fb.asp?m=4233072

 

From what I gather a 65mm works transparantly with a 100% stock efi fox 5.0, meaning that it supports demand and will allow silky smooth (as smooth as factory anyway) drivablity, therefore it stands to reason that a larger CI situation could use a larger TB than 65mm

(assume all TB recommended are new and high quality)

 

In theory, charts and others experiance are very helpfull, they can guide and give a good idea - however sometimes the best way to find out if part A or part B works a bit "Better" on a given setup in the real world (during actual use) - is to try both parts.

also remembering that "Better" is absolutly about what your personal desires are.... getting the car to do more of what you wish it to do; max smoothness, max drag racing times, max MPG... could all be "better" depending on your desires

 

Here's another one from Accufab. They are saying bigger, too big,won't hurt but it won't help on a dead stock to nearly stockengine.

http://www.accufabracing.com/article%202.htm

 

I am drag racer and my car ispurpose builtaround drag racing. I want to get form point A to point B as fast and smoothly as possible. I threw fuel mileage anddrivability, within reason,I still street drive it, out the window. So maybe a 75mm will do a touch better.Besides dropping weight (K-member kit, loose a/c,etc.)there are few bolt-ons left for my ride.

 

from what i have learned on "built motors" drag oriented what "I" have planned for my car allow all the air you can into the motor if anything will be a restriction it will be the intake or heads.

for street cars where they would just bolt on the larger tb and not tune the car for the extra incoming air this may not be the best idea. with that being said i think the accufab chart is good to base your opinion on for "your goals"

 

That's a good writeup, seems to go against what most people think is best though.

 

do the 75 and if you have a buddy with a 70 see if you could borrow it (buy them a new gasket) and see the difference?

 

i honestlty think that you would benefit from afr 185's and i'd keep the 75