Years ago I had a '67 SW chevy pickup w/ 250 stocker, only mod was hedmans/flowmasters. I used the old common 585-600cfm holley w/ vacum secondaries - worked fine. Also used a holley "Economaster" ( an economy replacement for a Q-jet) I believe it had mech. secondaries- it was only 450 cfm. it was for a 350 chevy Q-jet replacement, but I found the same basic carb was used with some mods as a buick V6 replacement -I approximated those changes (mostly idle circuit ports) to mine and it was a fine street carb. Point being, dont sell your 6's carb handling capabilities short. I would rather have a progressive 4 bbl. than a full time 2 bbl. The large 2GC rodchesters that would have been on those Oldsmobiles had 1-11/16 throttle bores and 1-3/16 venturis(in the mid 250 cfm range in four bbl talk). Try to find Doug Roe's Rodchester carb book-it tells all about almost all rochesters from BC one bbls to Electronic dual jets- HP is the publisher, he cfms a lot of rochesters. Two bbl cfm's need to be multipled by approx. .7 to equate to standard 4 bbl talk-thus the old holley 2bbl 500 is only about 350cfm when compaired to a 500 cfm 4 bbl. By the way, my old 250 would'nt rev much past 5000 in neutral, off a cliff! But the 4 bbls did made a difference-would'nt trade them for a stock one bbl or a two bbl for anything.
