Inches is inches, be they inline or side by side.
for a 250 (close to a 265 V-8) or a 302 (close to a 283,289,292,307,312, etc.) All are good starting points to adapt to our sixes. Use the latest (Up to and including 1967) for best power valving and smoothest operation....1968 and later begin have many concessions to smog control...making adaptation to the sixes more difficult in the ways of drivability especially for the automatic cars where you don't have the ability to "feather' the clutch to prevent a stall or a stumble. With Doug Roe's Rochester book in hand the Q-jet is everything you could need in the way of a single carb. That book will tell you how to modify every circuit in it, both smog and presmog models. 750 cfm should be plenty for any six. This carb was used on 500 inch Caddys...down to the 230 inch Pontiac OHC--Doug Roe ran one on the four cylinder Baja mini Boots. We have a member in the North Texas Chapter running a Q-jet on a pinto four cylinder 1600 (100cubes)maybe I'm lying-it may be a 2.0 liter. The secret is the tiny primary barrels--the 2.25 back barrels only come in as needed by the adjustable air valve--every thing adjustable on the Holleys is also adjustable on the Q-jet with Roe's book. I've seen Q-jets at the swap meets for as little as five bucks--you can't beat that, the same primary size of a 390 Holley with a bonus of 360 more air flow controlled cfm. This would be my choice for size, flexibility, and price.....just sayin'
