Anyone have an educated answer as to why Ford tried three different carburetor designs before fuel injection came out? I'm talking about (first) side draft. Then updraft on Model A,B, and C, and finally down drafts. I think the down drafts probably required a fuel pump, so that explains them.
Instead of Ford, Terry, the industry moved to progressively more reliable carburetors. Most of the changes have to do with performance. Changing airflow direction as little as possible is the most efficient way to fill the cylinders. Air / fuel mixture fills the cylinder most efficiently if the entry route is as direct as possible. Over time carburetor designers continued to find better ways to make carburetors meter air. With side draft and updraft carbs the airflow sometimes made 360 degrees of direction change before it reached the cylinder. That hurts performance.
It is still very hard for fuel injection to make more power on a dynamometer than the best racing carbs at steady speed. Electronic fuel injection has a multitude of advantages at anything other than steady speed.
Downdrafts are easier starting than the others, as gas vapor is heavier than air, so won't drop out of the manifold.
Even the Packard Twin Six, with the carb up between the banks, used an updraft, and they had to pressurize the fuel to feed that one. However, I, too, suspect it was the reliability of fuel delivery that dictated against downdrafts before 1929.
I agree with what Royce and Ralph said and had those thoughts before posting this. I figured Ford's reason for using a simple puddle type side draft on the T, was for economy reasons (Ford's economy; not M.P.G. economy for the consumer.) Then he turned around and used an updraft on Models A,B, and C. By the time the B and C came out, Ford was already using a downdraft on his V8's. A one barrel Detroit Lubricator on the 32 and a two barrel Stromberg 48 on the bulk of the 33 and all of the 34 models. If down drafts were available from 1928 to 1931, it would have taken a crazy, insane, old coot to use a updraft, when a downdraft was available. Everyone knows it was Henry's way or the highway; nobody better than his son, Edsel.
From what I've read here, Chrysler was first with downdraft in 1929. It was adopted later by others. Franklin still had updraft until the end in 1934.
When the fuel leaks out of a carb in the garage, the gas flows from updrafts and sidedrafts onto the floor. With downdraft, it goes into the engine; not near so unsafe.
Gravity feed means unlimited fuel to wash the garage floor.
Other than low profile mounting between cyl banks, - and safety - I've never heard that downdraft give better performance.