The Carburetor Shop LLC
204 East 15th Street
Eldon, Missouri 65026
Aftermarket carburetor adapters (updraft)
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.
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:
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.
(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.
(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.
(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.
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):
Carburetor and flange sizes (link to a listing of S.A.E. and other flange sizes).