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I'm sure this has probably been discussed before, but if you put the 56 2x4 setup on a 55 352, what will be the outcome? Or if you put the 55 2x4 setup on the 56 374, what would be the outcome?
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As venturi size (air flow and velocity) and jet size (fuel flow) are established within a carburetor for specific engine size and performance parameters, I'd expect that even though the difference is only 22 cubic inches you'd get less than ideal"
From 352" to 374" is only a 6% increase in demand and well within the physics of carb flow to handle. i doubt the two engines would notice any performance difference. The changes to '56 were mainly for fuel economy and daily driving.
In 1956, for example, the Packard Carribean used two 450 CFM Rochester 4Jet carbs versus the other seniors using one rated at 486 CFM. The 2x4 front venturi were slightly smaller and the jets are also smaller.
However, from experience, using two well-sorted single 4-bbl carbs works OK. On my current installation, the air/fuel ratio at cruise is dead on stoichiometric, at 14.7.
In fact, the major difference between the single carb and the 2x4 has to do with fuel economy on idle and decel. The single 4-bbl has idle circuits front and rear. Using two of them means having eight idle circuits. This makes the air/fuel ratio at idle difficult to tune and worse, goes dead rich on decel. The real 2x4 carbs eliminate the secondary idle circuits to lessen the giant sucking sound.
While the Packard throttle linkage opens both carbs, some 2x4 carb setups use a progressive linkage where most driving is done on the primary barrels of the rear carb. At about half throttle, the front two of the front carb open. If held full throttle long enough to a high enough RPM, the secondaries of both carbs open.
jack vines
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