B Davis

I have been told that the best size throttle body to put on a stock gt is 70mm...My question is ,wat will happen if I Put a 75mm on it.Im asking because the throttle body im wanting in polished chrome only comes in 75mm..Just want to make sure Im not going to screw my air to fuel ratio up...Thanks

Nuke

Stay away from aftermarket TB's, period, at least on the S197 (you ARE posting in the 2005-2010 S197 forum). Unless you're FI or internally modded, the stock TB is more than capable of feeding whatever air the engine requires. You'd have to bore and stroke (and possibly open up the exhaust some) before a larger aftermarket TB will provide good gains.

Aftermarket TB's have been known to have install problems; too high a % for my comfort.

DTMR

yeah i heard a lot of problems with aftermarket throttles EXCEPT for the ford racing one, others i heard they have been getting stuck open and stuff... ehhh scary

JCON

I have a ported and polished stock TB on my car. A little gain in response and it looks much better because it's polished.

Repzard

70mm Trick Flow on my 99 GT.
Plus other mods , No problems here and gained alot more throttle response.
over stock.

Throwing a 70mm or 75 mm on stock motor wont harm it.
Best man to talk to on this Forum is Cliffy K he will set the problem straight

Bpohlman13

The problem with going with a 75mm tb on a basically stock car, is that you will reduce the vacuum. This wouldnt be an issue on a Forced Induction setup, but on a N/A setup, you need the right amount of vacuum and right amount of back pressure. If your flow is too high, itll make the car bog. I suggest taking the stock throttle body off and sanding it and polishing it. You could also do the same to the inside of it so it creates less turbulance. Id also suggest getting a different plenum as that actually can be larger. I have an after market one and I ported it becuase there was alot of slag from when they made it.

Jay-rod427

The BBK 78mm combo TB/Plenum, prob didn't add any kind of HP gain, but absolutely improved low end throttle response.

!KLeech!

It wont hurt it at all, people for some reason just say that. Ive yet to ever see a car that didnt run correctly with a 75mm throttle body, including mine.

Bpohlman13

Ive had stock, 75mm and the bbk unit. As the larger aftermarket throttlebodies give better throttle response it tends to bog down on low end. At most, go with with a 70mm tb. Also, you get better throttle response more from the plenum and not the tb. Mainly because the stock unit is too small, and wont allow the proper airflow.

school boy

the 70mm is reconmended for stock n/a gt's buut a 75mm wont hurt anything. i had a 78mm throttle body and plenum in one from bbk and it didnt bog on low end