Carburettor balancing

[Shaun Pond]

I was shown another trick to help synchronize carburettors manually, without a carb sync device.

With the motor off, you insert short lengths of thin music wire (or any stiff bare wire; I've used straightened paperclips) through each spark plug boot at the distributor end, making sure that the wire contacts the metal end of the spark plug wire and that a short length of the bare wire is exposed at the top of the boot.

Then, with the car running, you touch a jumper wire to an exposed end to briefly ground or short out each cylinder, so that you may hear (or see, if you have a tachometer hooked up) the drop in RPM from each cylinder. Then you make your adjustments until each carb throat yields the same amount of "drop" in revs when shorted out.

This arrangement has the virtue of being fairly quick and cheap, and it's usable even with the air filter assembly in place.

This being the internet, I should probably also point out that, if you don't use care while shorting out a plug, you may inadvertently experiment with self administered electro-shock therapy as well.

Regards

[Ralph de Masi]

I have purchased the TwinMax and it works very well. I've connected it to the two threaded ports on the intake manifold but you will need to fabricate fitting because the ones sold with the TwinMax are too small if I remember correctly. The device is used more on motorcycles. If the carbs are off the motor I've also used the diameter of a drill to set the two sets of butterfly valves to the same measurement. That got me so close in one particular instance that I didn't even have to make adjustments with the TwinMax afterwards. Once the carb to carb synchronization is done I tend to use the Gunson Colortune to get the idle screws in range.

[john tynan]

The colortune is brilliant for setting the idle mixtures. It also helps to show if your spark is breaking down or if you have ignition problems. I am tempted to buy another 3 of them, as swapping it between cylinders is time consuming.