Re: 90mm Throttle Body
Just my opinion but only needed if you plan to exceed 15,000 rpm. There is a big difference between a six and an eight cylinder engine and not just the displacement. The intake and exhaust pulses also overlap. It is really better to treat a V8 as two independent fours that happen to be coupled together.
A six OTOH has an even set pulses particularly if a 60 degree V6 or inline. (A 90 degree V6 like the Buick 3800 is a kludge that needed an offset crank to work properly). As a result a six does not need a big plenium to smooth out overlapping pulses unless you are planning on a really wild cam.
What I would suggest is to monitor the manifold vacuum (just need a dongle, smart phone and Torque) and make a few full throttle passes. As long as the vacuum stays close to zilch you do not need any more intake area. (and 74 mm should be good to about 9,000 rpm unless something odd is happening. Is that enough ?)
I suspect you would be better to spend the money on the gozouta rather than the gozinta.
ps Back in the day I opened up the venturi of a Rochester injection to 62 mm and that was enough to get a B/Prod 327 'vette protested often.
Last edited by Padgett; Nov 19, 2013 at 01:37 PM.