First Downdraft Carburetor

[West Peterson]

There was a thread in another forum wanting to know what car company first used downdraft carburetors. I proposed that Marmon was the first to utilize downdraft induction on their 1927 Model L "Little," but since there weren't downdraft carburetors in 1927, they devised a way of using an updraft carburetor. It was one of the most powerful cars in the industry at the time, leading the carb industry to start building downdrafts.

Does anyone have an answer as to who used the first downdraft carburetor, and what company built the carburetor?

[1937hd45]

Does the 1926 Miller that Frank Lockhard won Indy with in 1926 count?

[Aanderson44]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">There was a thread in another forum wanting to know what car company first used downdraft carburetors. I proposed that Marmon was the first to utilize downdraft induction on their 1927 Model L "Little," but since there weren't downdraft carburetors in 1927, they devised a way of using an updraft carburetor. It was one of the most powerful cars in the industry at the time, leading the carb industry to start building downdrafts.

Does anyone have an answer as to who used the first downdraft carburetor, and what company built the carburetor? </div></div>

For starters, I believe the very existance of updraft carburetors was dictated by the use of gravity feed fuel systems (and even the vacuum fuel delivery systems required a large reservoir mounted high above the engine on the firewall--so they were really gravity feed as well) needing the carburetor to be well below the level of the gasoline tank (or the vacuum system's reservoir).

With this in mind, it seems to me that downdraft carburetion had to wait until the advent of reliable mechanical fuel pumps did it not, due to the sheer height of inline engines of the day? I believe the first mass-produced mechanical fuel pumps were those from AC Division of General Motors, coinciding with the introduction of the inline 6 "Stovebolt" engine by Chevrolet in 1929, which probably dates that fuel pump's introduction to at least late 1928. Ford, of course, stayed with updrafts and gravity feed with Model A, and the Model B 4-cylinder of 1932-34, but I think the B had a fuel pump due to the low mounting of Model 18 gas tanks at the rear of the chassis, but Ford's V8's had downdraft carburetion from the beginning (Detroit Lubricator in '32-'33, Stromberg's famed 2bbl downdraft coming in '34.)

I suspect a search of the development of the fuel pump and carburetors designed for use with mechanical fuel pumps would likely turn up something.

As for race cars, once the racers discovered the idea of pressurizing the fuel tank with a hand-operated air pump, downdraft and side-draft carburetors became the norm (Frank Lockhart must have had his hands full at Indianapolis in 1926!)

Art

[Guest boettger]

The following is an excerpt form "The Birth of Chrysler Corporation and Its Engineering Legacy" by Carl Breer.

"Pioneering the Downdraft Carburetor

One day in 1928 Everett Sheppard, an early development engineer with Holley Carburetor Company, came in and said, ?I would like to discuss some downdraft carburetor ideas with you.? All carburetors then were updraft except for a few horizontal or side draft types.

A downdraft carburetor concept would be ideal because gravity forces would accelerate rather than oppose the flow of liquid fuel particles, and they would be distributed better with less air velocity, producing more power. There would be little or no pockets for fuel to accumulate. My only question concerned cold engine starting. What would happen if an engine over-choked? We certainly would have difficulty starting it, once flooded, especially if it were an ?L? head engine which had a reservoir capacity that conceivably could half fill the manifold liquid fuel. (This we later resolved by placing an automatic drain check valve the lowest spot in our manifold.)

Sheppard had a prototype that he had been developing on a laboratory flow stand. He was attracted to the idea of using a flexible diaphragm for the gasoline feed in place of the gasoline reservoir float chamber still universally used today. The diaphragm idea looked attractive to us because of its compactness and casting simplicity.

We had hoped to have the downdraft carburetor perfected for the 1929 models. Our first spot checks looked very encouraging, but Shep?s diaphragm idea complicated carburetion clean up. It also brought in variables and unknowns. To be certain we would not be caught the last minute, I said to Shep, ?Would it agreeable if we brought Stromberg in to develop a downdraft carburetor using a float chamber as insurance in case the diaphragm idea did not work out?? He agreed, which was a good thing because Shep never did resolve the diaphragm riddles, and we finally had to release the Stromberg. It was only a matter of time before all other car makers turned to downdraft carburetors, and I doubt if you can find any quantity car producer today that is not producing vehicles with downdraft carburetors."

To this end I know for a fact that my 1930 DeSoto Model CF 8 Cylinder has a Stromberg DX3 Downdraft Carburator. This Carb was used on the 1930 Chrysler, 1930 Desoto and 1930 Dodge.

Scanning thru the Hollander's Interchange Book I don't see any downdraft applications earlier than 1930. 1930 appears to be the woodshed year as many 1930 autos show downdraft carbs.

FYI: the 1928 - 1931 Marmon show a Stromberg UX-2 which is a 1 1/4" flange updraft carb.

[oldford]

From the "Histomobile : The complete online car specifications database." I found this gem: 1929: Chrysler adapts the more efficient downdraft carburetor. Now I don't know if this was the first use of a downdraft carburetor, but this indicates that this was the first year tha Chrysler used the downdraft.

Frank

[ronbarn]

The Model L Marmon indeed used an updraft carb with vacuum tank pump. The intake manifold did indeed route the flow of the fuel mixture to a position above the cylinder intakes, but that was Marmon's method to make the distance of fuel flow equal for each cylinder, thus assuring that all cylinders had equal fuel allocation.