IH carburetors assemblies differences

[staninlowerAL]

There are 4 different carb assemblies listed in ENG-1 and TC 131 parts listing for cub and 154 number series tractors:
Farmall Cub -- 251 234 R94 replacement 63 349 C91
International and LoBoy Cub -- 364 579 R91 replacement 63 349 C91
Number Series 154 -- 405 004 R91 no replacement number listed
I am aware of different designed parts that require a different assembly number but for the FCub/LoBoy/International Cubs the conclusion is that the 63 349 C91 carb is OK to use as a replacement for the earlier assembly numbers; however, I cannot find a replacement assembly listed for the 154 carb assembly 405 004 R91. I know from experience that the other 3 carbs will fit and function on the 154 manifold but wondering why there is no recommended replacement information in the parts lists. I do know that there are probably some internal differences like jet size, air bleed, venturi, etc and the 154 carb has a different choke shaft. I would like to know more if anyone can explain more differences on the details. Thanks, Stan

 

[Jim Becker]

The Cub Service Manual (section 2 - governor/fuel, in the resources) has the jet sizes etc. for the first 2 numbers you mentioned. I think the C91 number is for a Zenith replacement.

 

[inairam]

The 405004R91 has a larger throat area. I have one or two. I only use it on the later Cubs. I think it was used on the 154 but most of the later ones had Zenith carbs. The other difference is the choke cable vs rod styles. The IH style can be converted to rod style. The replacement if you can not find a 405 is to convert to a Zenith

 

[staninlowerAL]

I have a C91 and need to check the throat size, it may be larger as Jim indicated. Stan