John Cooper Garages Metro Cooper Twin HIF4 SU Carbs Reconditioned



When Barry Tilbury, a well known enthusiast and expert in the Classic Mini scene first told me that he had found a Cooper Metro (or should it be Metro Cooper?) I did not really know what to think. I have been around classic cars for all my working life but had never heard of such a thing! As you can see from the picture above, it does exist, although this is believed to be the only surviving example of the model.


He told me that it uses a weird twin SU carb setup mounted on a Weber style manifold which we believe to have been made by Janspeed, who were a very well known tuning company at the time this car was produced.

janspeed logo

Anyway, his problem was that although the car was running sort of ok, one of the carbs was leaking fuel, which being above the exhaust manifold could have been devastating! A few pictures later, and I identified them as being Twin HIF4 1.5″ SU carbs, as used on the MGB from 1972 on. They had clearly been modified to suit the unusual installation, and obviously had issues, so I advised him to bring them in for me to take a look.


These carbs would once have looked fantastic in the Metro Cooper engine bay, but they were now, quite frankly, in a terrible state.

Cooper Metro Engine Bay Twin HIF4 Carbs
original engine bay photo photo provided by Barry Tilbury

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I partially stripped them while he was here, and quickly found the cause of the leak, a worn out needle valve, the consequences of which are over pressurising of the fuel chamber, and fuel pumping out of the overflow outlets.

Typically, the overflow outlets are connected to pipes to transfer any leaking fuel away from the engine to reduce the risk of fires, but the unique arrangement of these carbs meant that fitting such a safety system was not possible. Remember, this conversion was built as one of a series of prototypes, and never went into mass production, or I am sure this issue would have been solved.

While dismantling, I found several other issues, including play in the throttle shafts, one seized and one broken rose joint on the throttle interconnecting linkage, brittle choke seals and so on and so on.

john-cooper-garages-Metro-cooper-prototype-reconditioned-restored-twin-hif4-su-carbs-fixacarb-08 The owner of the car, Chris Dawson, who was the former service advisor at John Cooper Works, was contacted, and he quickly agreed to have the carbs and manifold fully reconditioned back to their former glory.

The carbs were fully stripped, all cast components professionally vapour blasted, including the manifold. A genuine CRK116A twin HIF4 SU rebuild kit was allocated, and new rose joints were sourced. Sourcing the rose joints was actually the most challenging part, as they are hard to find with imperial threads now. Barry searched ebay and came up trumps, so we were able to continue the project.

The manifold was bolted to one of our 12G940 cylinder heads, as this made the assembly easier to work on while building the carbs up again and setting up the throttle linkage.


The dashpot tops were polished, assembly completed and the carbs were reset back to factory settings. The interconnecting linkage was carefully set to ensure that both throttles could close fully, as well as reach maximum throttle at the same time.

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If you are interested in finding out more about this car, we found the following resources online:!/

The owner of the car, Chris Dawson, runs the popular John Cooper Garages club group on facebook which can be found here:

If you are interested to find out more about this project, or to discuss your own, please contact us on [email protected] or 07875300056. Alternatively, please use the contact form below.

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