When you work on multiple engines for dyno testing and other automotive adventures, carburetors can often end up sitting around in storage for long periods before they are once again called on to perform. We’ve had problems with some of our carburetors that were generally caused by pump gas remaining in the float bowl that eventually evaporates.
This may not seem all that bad and not every carb is afflicted the same way. In one case, the accelerator pump diaphragm became brittle and cracked and started leaking. In another case, the power valve diaphragm failed and in a third case the O-ring sealing the needle and seat to the bowl shriveled up and started leaking. A current popular scapegoat attributes all these problems to the ethanol that is currently mixed at 10 percent by volume in most pump gas.
We’re not going to dispute that pump-gas ethanol may be the cause of some problems in some applications. But with these issues, the cause is a wholly different chemical. The real cause of these problems is fuel additives called aromatic compounds that are mixed at between 18 and 25 percent of nearly all pump gas sold in the continental U.S. These aromatics are a combination of benzene, toluene, ethyl-benzene, and xylene — often shortened to BTEX. These are all nasty chemicals that can cause difficulties for rubber-like components such as the fuel pump, accelerator pump, and power valve diaphragms, rubber O-rings, and other components throughout the fuel delivery system.
These BTEX chemicals can dry out the rubber and cause it to become brittle and fail. Our friend Sean Murphy at Sean Murphy Induction (SMI) has seen many of these issues. When it comes time to store your car for the winter or to store the carburetor on the shelf, he recommends draining the float bowl by removing one of the lower bowl screws.
With the fuel removed, replace the bowl screw and shoot WD-40 with a nozzle into the vent tube for both primary and secondary bowls. He says the WD-40 will absorb any water in the bowl and will also coat the materials in the bowl. Pumping the accelerator pump a few times will help lube the accelerator pump diaphragm and extend the life of the power valve as well.
Another idea is to extend the life of the needle and seat seal by coating it with light oil. If the seal fails, Bo Laws Products sells these O-rings individually because, currently, Holley does not offer an individual part number for these O-rings.
This simple WD-40 step also helps minimize damage from what is often called “White Death” or aluminum oxide. This is that nasty white stuff that can be seen in many stored carburetors. Aluminum oxide forms after the fuel has evaporated and the remaining water corrodes the aluminum in many carburetors. This WD-40 idea only takes a few moments and might just help extend the life of your favorite carburetor.