?!?Syncronize Your Carbs With A Stethoscope?!?

Man using stethoscope

Yes it's true, balancing the air flowing through your carburetors using a pneumatic stethoscope. Many years ago people did not own fancy gadgets such as vacuum gages to use while measuring the air flowing through SU type carburetors. If a set of SU carburetors needed an occasional adjustment, the owner would simply pull a short length of rubber hose from the boot of their car or tool box, and tune them very ear. I learned this method years ago from an old timer, and I liked it so much I haven't used a vacuum gage since.

Although, I have since found a better alternative to the old rubber hose method. A common airline headset does a wonderful job. This is the very same headset that you would use while listening to music or a movie soundtrack while flying on board a commercial airline. The sound waves are carried through the hollow tubes going to each ear. The very clear "stereo" sound created by the air flow sucking from the caruretor, then passes through the tubes in the same way. The sound is so clear through the head set that while very slightly adjusting the air flow, the difference is very easily and accurately detected when the change has occured. By comparing the sound at each carburetor while making the adjustments, you can easily set the air flows to be equally matched.

It is very important to maintain an equally balanced air flow through each of the two or three carburetors for your engine to perform properly. Some carburetor's are situated in a very awkward location due to the lack of engine compartment space. Therefore it is very hard to place the vacuum gauge over the intake of the carb and get your head in a position to take an accurate reading at the same time. I've found this to be the case with my MGA, where the intake is in a very tight spot and it is nearly impossible to see the indicator. Using the stethoscope allows you to stick the hose just inside of the intake opening, and listen to the clear sound while making changes to the adjustment.

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