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MG MGA - Carburetor Question

I have been wrestling with an issue regarding my 58 1500 rdstr. The PO installed a 32/36 Weber 2 barrel downdraft on a matching manifold.

I have the original SU H4 carburetors that were included when I purchased the car. I'm quite certain they need to be rebuilt. The car starts every time, and performs flawlessly with the Weber; I am jut wondering if I'm sacrificing a significant amount of top end performace by not installing the SUs?

The car has recently been refurbished as a beautiful driver, and this is why I am comtemplating reinstalling the OEM carburetors.

Arguably, the Weber is not as sexy looking as the dual SUs, but at my age, I don't have the patience for a lot of carburetor foreplay to induce the ultimate pleasure of driving her.

Anyone using a Weber out there?

F Valenzano

Not used the downdraft weber (I have always chosen the sidedraft) but I do know it well. I also know the SUs well and my advice would be if the weber is set up well then leave it on. For everyday use it is far superior to the older SUs.
Bob Turbo Midget England

I fitted the Weber carb in the mid 90s after fighting my worn out SUs since the early 70s. Never have had a problem starting the car since. engine response is fine.

How is your throttle cable routed and fitted to the carb? The stock throttle cable is too short (at least mine was) for the inner cable to pull the carb actuator. I currently have mine set up to "push" the actuator.

Don Carlberg
Don Carlberg


In order to facilitate the Weber more efficiently, I turned it around so that the throttle actuator on the carb lined up with the stock throttle cable location. I fabricated a a piece to anchor the throttle cable, which allows it to work as designed with a pull motion when the accelerator pedal is depressed, just like the SU set up.

See photo.

F Valenzano

Here's a closer view

F Valenzano

It looks as though the choke cable is long enough to facilitate this installation as well. That would put the vacuum advance away from the engine and the fuel connection closer to the firewall. It's only a few cap screws - I may try your configuration. How did you configure the throttle return spring? Thanks for the photos.

Don Carlberg

Does anyone know how the downdraught twin choke weber (is it a DCD Fran ?) performs on the MGA as compared with twin SUs?

The manifold shape looks like it will give far better gas flow than the twin SU design with its tortuous looking manifold and connecting tube set up.

Wouldnt one much bigger SU with a similar manifold to the one shown above flow better than the std twin SU design?
I wonder if anyone has ever done this.

Many years ago I had an after market twin choke 28/36 DCD Weber fitted to a Ford Escort 1600 and it made a significant improvement in performance (approx 10%)
So I dont think you can go far wrong in leaving the Weber on the car Fran, especially if it is working well.


Colyn Firth

You are exactly correct. Turning the carb around puts the fuel connection next to the heater shelf and the vacuum line away from the motor.

I used the stock throttle cable. The throttle return spring is an integral part of the carb body. If you look closely at the center of the photo you can see the spring running vertically.

The manual choke cable was run under the carb body and looped up and around to the lever.

F Valenzano

This thread was discussed between 04/01/2011 and 05/01/2011

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