THE CARBURETOR SHOP / Carburetor adapters

The Carburetor Shop LLC

204 East 15^th Street

Eldon, Missouri 65026

Aftermarket carburetor adapters (updraft)

General

In the 19 teens and twenties, many carburetor companies made aftermarket carburetors for many applications for which they had not sold the original carburetor. As many companies either ignored, or blatantly defied, S.A.E. standards, it was necessary to sell a flange adapter with the aftermarket carburetor.

I have lists of adapters originally produced by Carter, Marvel, Rayfield, Schebler, Tillotson, and Zenith (and probably others). No, I will not publish these lists for a number of reasons; the primary reason being they would be mis-interpreted by many.

How? These adapters were made to adapt a SPECIFIC carburetor to a SPECIFIC application. So a Zenith adapter to adapt a Zenith size 2 type 105 carburetor to a specific application MAY NOT adapt a Zenith size 2 type 63AW carburetor to the same application. Why? Because the 63AW is physically wider than the 105. So looking at any of the lists for a cross-flange size 2 to size 3 adapter would get an enthusiast a part number for an adapter that would bolt to the carburetor and bolt to the intake, but maybe NOT allow the carburetor to fit in the allotted space between the engine block and the fender.

Fabrication

So, the way we suggest to proceed:

(1) Determine which carburetor to use to properly run the engine.

(2) Determine which type of adapter will be necessary to adapt the carburetor to the engine:

(A) straight

(B) cross

(D) offset

Each of these will be discussed in detail below.

(3) Determine the dimensions of the carburetor with the adapter connected, and measure to see if it will fit.

Types of carburetor flanges:

(1) straight - a straight line drawn from center to center of the mounting studs would run from bumper to bumper on the vehicle

(2) cross - a straight line drawn from center to center of the mounting studs would run from fender to fender on the vehicle

(3) rotated - a straight line drawn from center to center of the mounting studs would not be parallel or perpendicular to a straight line from bumper to bumper. Good examples would be 1929~1931 Chevrolet 6 cylinder and virtually all single barrel Marvels produced after about 1925. The Chevrolet is rotated 30 degrees. The Marvel rotation varies.

Types of adapters:

(1) straight - the straight adapter will allow a carburetor with a straight flange to mount to an intake with a straight flange. Often this is quite easy. From a swap meet (or salvage yard if you are lucky enough to still have a salvage yard), acquire two unloved carburetors (we used Tillotson type JR, Holley 1904, and Rochester type B and BC) with cast iron flanges with the appropriate center to center spacing, place the throttle body in a power hacksaw such that the saw will cut the throttle body parallel to the flange just on the side of the throttle plate opposite the flange, acquire a short piece of steel pipe of the appropriate diameter, and weld it (or if you are me, take it to someone that CAN weld) all together. The completed adapter should resemble a capital letter "H" that fell over on its side. The cross-bar in the "H" is the pipe with an I.D. equal to the smaller of that of the carburetor or the intake. There must be sufficient distance between the legs of the "H" to allow nuts to be installed.


This is a new old stock Carter straight adapter	Note in the upright position that the adapter resembles the capital letter "H". This adapter adapts a smaller carburetor to a larger intake. Many of the early carburetors were horribly inefficient, and a smaller more efficient carburetor could replace the original.

(2) cross - the cross adapter will allow a carburetor with a straight flange to mount to an intake with a cross flange. Theoretically, the reverse is possible, but cross flange aftermarket carburetors are very rare. Because of the orientation of the nuts, often a cross adapter may be made as above but without the pipe; just weld the two flanges together.


This is a new old stock Carter cross adapter		This is an adapter we fabricated. At one time, we sold lots of these. We had a mold made, had castings made of aluminum, and then machined. Note this adapter is much shorter that the original, thus does not impact the amount of vacuum necessary to pull the fuel from the carb to the intake.

(3) rotated - the rotated adapter will adapt a straight flange carb to a rotated intake manifold. Often, like (2) above, it may be fabricated simply by welding two flanges together.


This is a new old stock rotated adapter. Difficult to see in this picture, but if one looks closely, one can see the end of the bottom flange at 12 o'clock in this picture

(4) offset - the offset adapter, virtually always identified with Marvel applications may be necessary because using another adapter will cause interference with something (generator, steering box, etc.). The most common requirement for these is the 1926~1929 Buicks where one needs a rotated adapter WITH an offset. Basically, the offset is a small "S curve" in the pipe connected the two flanges.


This is a new old stock Carter offset adapter. This one was designed to mount a Carter type BB-1 carburetor to a 1926~1929 Buick.	Difficult to see, but note that there is as upward slope from left to right of the right side from the left. This is another adapter we once reproduced. Have replaced at least 150 1926~1929 Buick Marvels with Carter, Stromberg, and Zenith carbs.

All of the above assume a two bolt flange. There were a few applications with 3, 4, 5, and 6 bolt flanges. The procedure is the same. S.A.E flange sizes (cheerfully ignored by Marvel, and some others):

(5) Special

This is a special adapter, which doesn't fit any of the above types. It adapts an updraft carburetor to replace the Stewart (Detroit Lubricator) on the Essex.

Carburetor and flange sizes (link to a listing of S.A.E. and other flange sizes).