tried searching, but didn't come up with much. we are Looking for some advice on TB size. I'm building a friend's road course motor and am looking for the best power under the curve from around 4000 to 8500rpm. We really don't want to rev higher than that.

Motor is an 11:1cr 84.5mm bore ITR motor. head is stock, other than a valve job.
skunk2 Pro IM or performer X intake manifold (waiting to measure)
skunk2 pro1 cams.
4-2-1 header w/ 2.5" collector (forget the brand)

We would rather trade a few top end hp for a fatter midrange with better throttle response. At first I thought a 68mm might be too big, Although now I'm thinking a 2.0L could support that size and still have good midrange.

I've always been wary of "bigger is better", so what does HT think?

 

Mike,
I would recommend a tapered bored throttle body with a 68mm opening to 65-64mm at the butterfly.
HTH
-Gil

 

Your right to be wary of the "bigger is better" moniker that seems to plague online car forums, and the area of TB is an important area not to go overboard on. I agree with Guilotine, 64-65 at the butterfly is a good area, particularly with your desire for a strong midrange....going too large on the TB will dash those aspirations.

 

thanks for the info guys. So who makes a tapered TB?

everything I've seen just says 65mm, or 66. Where could I get something that tapers from 68mm to 65mm or 66mm?


thx

 

i agree with the tapered theory, and good luck with the build!!!