by Art Gardner
Many of you may have rebuilt your 1949 Cadillac carburetor, the trusty Carter WDC 722S. Although the instructions in the Shop Manual are very good, in paragraph 10 on page 124 there is insufficient detail on an important tuning trick: aiming your accelerator pump discharge jets for optimum throttle response. The Carter 722S carburetor has two little dots cast into the carb body and the sprays from the accelerator pump jets are supposed to hit these targets. The Cadillac engineers figured out that when the spray hits these targets you get the best atomization of the accelerator pump spray and thus the best throttle response.
This tuning can be done while rebuilding the carburetor or simply by removing the air horn (the very top of the carb) to gain access to the accelerator pump jet nozzles. Indeed, once you take off the air horn, you have good access to the nozzles. The targets are little dots cast into an upper portion of the lower half of the carb. You just take a pair of needle nose pliers and gently bend the jet nozzles until the fuel sprays directly onto the “targets”. If there is fuel in the carburetor bowl, manipulating the rod from the gas pedal a little causes fuel to be sprayed from the nozzles and you can see if it is hitting the targets or not. The carburetor does not have to be totally disassembled or even removed from the engine to do this.
So on my own car, I removed the air cleaner and the air horn from the top of the carb and tweaked the aim of the nozzles to hit the targets exactly. It really made a difference. We also did this with Jay Friedman’s car and he reports that his car is running better than ever as a result. By the way, I didn’t figure this out myself; I found the details in an old carburetor user guide.