One of the newfangled gadgets we're using on complex vacuum systems now would also be useful if you do have a vacuum leak. It's a "smoke machine" that diagnostic techs are using to pinpoint tiny vacuum system leaks that trigger trouble codes on the computerized jobs. By introducing smoke into the intake under a low positive pressure with the engine off and tracking down any leaks, it's possible to find even very tiny ones. A major leak shows up in a hurry.
Another way to go about finding a leak involves backing off the intake valve adjusters until they're all closed and putting a couple of PSI of air pressure into the carburetor air horn with an air hose and a pressure regulator, then listening for leaks with a piece of rubber fuel line used like a stethoscope. I adapt a piece of radiator hose to the carb top, and bush the other end down to accept a quick-connect for my air line. Low-tech, but it works.
Jerry
Last edited by Hotrod Lincoln; 10/13/2010 2:20 PM.
