In my high school days I tried the 2bbl to 4bbl adapter on my 68 305E. I installed a Holley 780 dual feed square carb bore. The idle was fluctuating up and down
, seemed like the adapter wasn't sealing well, don't think the vacuum secondary's ever kicked in
. A couple years later I decided to try the Economaster Holley 450cfm mini spreadbore carb with the same adapter
, when the secondary's kicked in there was a stumble
because there's only so much fuel you can squeeze through a small passage, both episodes only proved the Holley 500 2bbl prevailed with the stock manifold. If you're going to run the stock manifolds specially on the 702 and run 4bbl carbs then the best bet is to modify the stock manifolds to accept a 4bbl base like David Chadwell did several years back. You can't use the Magnum V6 intake manifolds on the 702 due to the spacing these engines have their own specific intake manifolds
