How does one select a multiple carburetor set-up for a stovebolt?
Well, the first consideration is to look at the intake profile of the cylinder head. These are arranged in three banks of two. So, quite obviously, a manifold utilizing three carburetors (one per bank) is going to be more efficient than one utilizing two carburetors.
An example: as a child, did you ever throw a rock in a pond? And watch the "wake" from the splash? Which was uniform. Then throw two rocks in the pond, and watch the two "wakes" where they intersected with interference? The fuel/air mixture in the two carburetor manifold has the same effect, where fuel and air from both carbs are trying to feed the center bank. It might be possible to divide the runners to the center ports, but I have not seen that done.
And this arrangement is why Jerry (Hot Rod Lincoln) throws big rocks at two single barrel set-ups
If the two carb set-up is done PERFECTLY, both in selection, and tuning, there is a wee bit of gain, both in power and economy; maybe from 5~8 percent. If done incorrectly, one can certainly lose much more percentage over a well-set-up single carb. Generally speaking, most dual two-barrel set-ups gain is either due to: (A) the mind of the owner (eye candy), or (B) replacing a mal-functioning single carburetor.
So pick two or three, this decision is left to the owner. As far as carburetor selection, I wrote the following 20 or so years ago, and while they might need tweaking, I wouldn't change much:
Selecting 2 carbs for a 6 cylinderSelecting 3 carbs for a 6 cylinderJon.
