Mark - the key to needing increased carburetion is in the modification of the engine.
For a moment, completely forget about carburetion (and ignition). Now what you have is an air pump; pure and simple, an air pump. Now paraphrasing the old schoolchild joke of how much wood can a woodchuck chuck into how much air can an airpump pump?
Well, this is a question with a answer.
CFM (at 100 percent volumetric efficiency) = (RPM times CID) / 3456.
Understand the above, and you won't have to remember.
You are dealing with cubic FEET per minute on the left; and cubic INCHES on the right. Thus to convert the cubic inches to cubic feet, you divide by (12 times 12 times 12) or 1728. BUT WAIT, as the TV commercial screams; with a 4 stroke engine, you only draw air on every other crankshaft rotation. So divide by 2. Multiplying the 1728 and the 2 on the right gives you 3456.
Note the equation is listed at 100 percent volumetric efficiency.
A good AVERAGE FOR STREET ENGINES:
Modern (1960 and newer) USA 6 cylinders maybe 80 percent
Older (stovebolt) 6's maybe 70~75 percent
Modern V-8 (Chevy 350) maybe 80~85 percent
Hi-performance V-8 (Pontiac Ram Air IV) maybe 90 percent
Now consider why one NEEDS more carburetion:
(A) the engine is modified (allowing a higher RPM)
(B) the original carb is too small (think taxi, very few others)
(C) eye candy
JW51, you asked about different methods of increasing carburetion if one needs it. Your suggestions:
(A) dual carbs with progressive linkage NO, NO, NO!!!
(B) small 4-barrel (most would choose this option)
(C) something else - OK suggestions:
(C-1) dual single barrel carbs with solid linkage
(C-2) triple single barrel carbs with solid linkage
As Joe H. suggested, multiple carbs on an inline 6 (properly done) even the fill ratio/cylinder making for smoother performance. This is the area of gain on a stock engine; but also applies on a modified engine. The multiple carbs somewhat improve the volumetric efficiency.
Jerry - which breed of duck???
Jon.
