[FilW]

Originally Posted by Dauntless

Yes, the usual equation is D=(CIDxVExRPM)/(IVx1130). Assuming very good preparation for your engine, that works out to:

D=(97x0.9x9000)/203,400=3.86" diameter (~98mm)

If the head work is not first class, use 0.85 for the VE instead of 0.9. The 180 in the second term is intake velocity in feet per second. 180 is a good number, but if you prefer another, go ahead and use it.

So, where does your present intake fall short?

Can you tell me what CID stands for?
why is the IV 180

or am I being thick