The Woes of a Fuel Fitting

99.99% of carburetor leaks are from a poorly installed fuel inlet fitting.  May we repeat that?  99.99% of carburetor leaks are from a poorly installed fuel inlet fitting.  As fuel drips from a bad seal between bowl and fitting, it WILL look like the fuel is coming from under the accelerator pump diaphragm or from between the main body and the base plate.  Rest assured, those two gasketed areas are too secure to ever, ever leak in a VDL carburetor.  Let’s look at some things that can go wrong:

1 – Be sure that the gasket is seated well in the register of the inlet opening of the bowl.  If it is cocked up on an edge, you will never get it tight enough and it will leak.  We have found that some of the thicker aluminum gaskets are a tick wide in diameter and may be tricky to position correctly.

2 – The majority of inlet fittings are made with the hex nut on the end closest to the bowl, and you know how difficult it is to get a wrench on that without rounding off the edges.  Perhaps invest in a new fitting designed with the hex nut at the far end from the bowl – very nice!

3 – Crossthreading is a big concern.  Damaged bowl threads can be chased with a 7/8 x 20 tap, but the solution is most often a new bowl.  So, a drop of light machine oil on the fitting’s threads will ease installation, and always start the fitting by hand to feel the proper alignment.

4 – The rigors of racing are hard on parts and require maintenance after every race or occasional replacement between seasons.  Monitoring the condition of all your fuel lines and fittings should be a part of that program.

If you feel like the inlet fitting is properly installed and you still find a leak, try this simple test to confirm that the leak is not the carburetor:  place the carburetor on a 2×4 on the bench so it sits level.  Fill the bowl or bowls with fuel and let it sit undisturbed for a short time.  If there is no evidence of fuel seepage, then the inlet is not properly installed.  At the least, replace the gasket and try again.  At the most, get a new fitting.