I would like to know, how do you determine the size of a throttle body? Do you measure inlet size or outlet size? Reason being is because I have a gude throttle body from an old racehead i used to have. I measured it and the inlet diameter is 61.9mm inside and the outlet is 69.8mm on the backside. When a aftermarket tuner makes a throttle body, do they advertise the inlet or the outlet? I'm just curious, because I am highly considering putting this thing on the turbo car.

 

hmm no answer yet... makes me wonder.