Hey there guys, I have a 72 Datsun 240Z with a E31 head on N42 block. I'm running Weber 40 DCOE triple side drafts power with a Crane cam 92 ignition. My motor bogs and stalls when I accelerate around the 3 - 4 k rpm range. I would punch the gas again and the engine would sound like its going to die. It was running fine a months ago before i install my air horns. It's also takes more attempt to get the car to start after sitting for more than 3 hrs. Could it be because my air horns are too long? 60MM for the total length of air horn. Or could it be an ignition issue? I'm still learning about my car as i spend time with it. Please, any input will be great!

0. Are the air horns the type that fit around the aux venturi? If so, did you accidentally misalign the aux venturi where the main fuel passage mates?

1. Check fuel level. It should be 25mm down from the shelf where the main jet assembly screws.

The air horn air are the type that slits into the venturi, so yes its fits around the aux venturi. All i did was slit them into the venturi opening and bolt them up. If you may please inform me on how i could have misaligned then the venturi where the fuels main mates?

The fuel level looks good at about 25mm.

Since you did not adjust or modify any significant parts of the carb or linkage, I assume the problem has to do with inserting the air horns:

There is not much that can go wrong except: The aux venturi has a passage for the fuel to flow to the main nozzle. The venturi's fuel passage has to mate correctly with the corresponding hole in the throat of the carb body. To do this correctly the locking mechanism that holds the venturi must be carefully tightened while at the same time ensuring venturi fuel passage alignment. (I believe some carbs use a clip retainer that may not adequately press the fuel passage surfaces together).

I recommend that you double check that all is aligned properly.

I'm with Blue, venturi misalignment was my first thought as well. Follow the given advice and report back.