Snowdancer
New member
When I bought my Imp (number 195) this summer, the previous owner also gave me a new Weber 34ICH carburetor. The old carburetor worked reasonably well except ran rough at idle (900 RMP) so rather than rebuilding it I decided to install the new carburetor and as a bonus with the Weber Carb I get a vacuum port which the original carb lacked
Unfortunately, the Weber is not a direct replacement as it longer and its fuel inlet structure interferes with the radiator return.
To fit the Weber my choice was to either raise the carburetor or rotate the carburetor 25 degrees counter clockwise to clear the interference. Vertically under the engine cowling I had less than ¾” to work with so raising the carburetor does not work.
I came up with an 0.4” thick adapter plate design that my son then milled for me on his CNC machine.
BTW, the new Weber performs great and I used the vacuum port to set the distributor timing.
Pictures:
Old Carb on the left and new Weber on the right. The Weber is shorter than the original carb but this advantage is lost as the air intake rink has to be mounted proud of the Weber carb top to give clearance for the Weber’s choke circuit. The air intake mounting ring has already been moved from the old carb to the Weber,
The Weber carb showing interference when attempting a direct replacement
The adapter plate and various parts required to rotate Weber 25 degrees
The adapter plate mounted to intake manifold. To get sufficient clearance had to grind off one corner of the water intake structure which you can see in the right side center of picture
Two views of the mounted Weber and a final view showing ¼”inch clearance under the engine cowling
Unfortunately, the Weber is not a direct replacement as it longer and its fuel inlet structure interferes with the radiator return.
To fit the Weber my choice was to either raise the carburetor or rotate the carburetor 25 degrees counter clockwise to clear the interference. Vertically under the engine cowling I had less than ¾” to work with so raising the carburetor does not work.
I came up with an 0.4” thick adapter plate design that my son then milled for me on his CNC machine.
BTW, the new Weber performs great and I used the vacuum port to set the distributor timing.
Pictures:
Old Carb on the left and new Weber on the right. The Weber is shorter than the original carb but this advantage is lost as the air intake rink has to be mounted proud of the Weber carb top to give clearance for the Weber’s choke circuit. The air intake mounting ring has already been moved from the old carb to the Weber,
The Weber carb showing interference when attempting a direct replacement
The adapter plate and various parts required to rotate Weber 25 degrees
The adapter plate mounted to intake manifold. To get sufficient clearance had to grind off one corner of the water intake structure which you can see in the right side center of picture
Two views of the mounted Weber and a final view showing ¼”inch clearance under the engine cowling
