sitruk

hey quick question concerning a throttle body upgrade. i currently just have the stock 60mm tb on my 87 gt with bbk cold air, was thinking of possibly upgrading to a 70 or 75 mm tb. would this give me more power? also my friend got a new tb for his bmw and its running richer now, would i have the same problem if i went to a bigger tb? thanks

302army187

will you gain power?

yea probly.

enough to FEEL?

i doubt it.

its a good mod to have, but if your close to stock your not going to gain much.

i would go with a 70mm.


and no, you wont start burning rich.

Timspony

65mm TB imo..........you'll be fine!

sitruk

would a 75mm tb be too big then for a baisc stock engine? i doubt i'll be supercharging or turboing it, maybe throw a new cam and pistons in later. . . .

Joel5.0

Nope.... just make sure the TB and intake plenum bore are matched. Check these before and after pics of a 75mm on a GT40 intake.

302army187

very nice joel!

my 70mm is perfect for my intake almost all the way around, then the bottom part of the intake is just SLIGHTLY bigger then the throttle body.

maybe one day ill even it out.

zippo2341

You would be fine with a 65mm, a 75mm on a stock intake might bottleneck the airflow when it transitions to the stock upper plenum. Bang for the buck wise its not really worth it on a stock motor, but will be a good supporting mod if you plan on doing motor work. however there are other mods out there that are more worth the money

Joel5.0

Care to explain?....

w8less

i agree lets here a little bit more of this

jthorn9

75 will be too large for your application, there's not any power difference between 70mm and 75mm peak hp wise, but 75 will lag down low, and you'll likely loose some torque. For a stock engine 65mm or 70mm will be just fine, but serriously, for the cost of a TB, you can put a modest down payment down on an intake manifold kit, or buy a used GT-40 intake and gain much more power than the TB will yield.