How to Balance Twin Carburettors

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In this ‘how-to’ video guide from Skill Shack, Ed Hughes talks you through a procedure which can be used to tune and synchronise twin carburettors without specialist equipment. As a result of watching this video tutorial, you’ll have the necessary skills to help you get your classic car’s engine running smoothly with increased power and reduced fuel consumption.

Nothing beats a classic car that’s running perfectly, but it can take a while to achieve this if the engine is out-of-tune. It involves juggling ignition timing, valve clearances and carburettor settings. Adding a second carburettor to the mix and the task becomes more complicated. So in this guide Ed demystifies the whole process.

In tuning an SU or Stromberg carburettor, such as the ones installed on our demonstrator MGB GT, we adjust the mixture at idle. This sets the height of the jet relative to the tapered needle. Therefore, it affects the mixture strength across the whole range of operation of the carburettor. Getting it wrong makes the car run badly all the time. Starting with a brief explanation of how the SU carburettor works, we learn the principles behind what we will be hoping to adjust on SU carburettors. Then, as part of a live demonstration Ed explains what to listen for, what to adjust, where to adjust it and how to know when you have your classic car’s SU carburettor tuning and balancing just right.