Alleycat has been having trouble finding a vacuum leak on his 292 so I thought how we do it (after easier methods have failed) might be a tip others can use also. It's messy and takes time but it WILL find the leak. First, back off the adjusters on all the intake valves till they are closed. I back the adjusters off in 1/4 turns and write the number of 1/4 turns down so each can be put back in the same position. Set the valve cover back on cause it's gonna get messy. Seal the top of the carb, I use an old piece of inner tube and a hose clamp. It is now a closed system. Hook an air hose to the wiper, power brake, dual action fuel pump, automatic transmission, or ANY vacuum port. Make a strong soap solution---as much as a cup of liquid soap to a gallon of water. Spray the solution over EVERYTHING. Two pounds of pressure from the air hose will make bubbles like crazy but I set the regulator at 10#'s as this has never damaged anything ( so far) and you can often hear the air escaping without making a mess with the soap. If you don't have a regulator unplug your compressor and drain the pressure down to 10-15#'s and use that way. Seldom had to use this method on something as simple as an AD truck but came in handy on stuff with vacuum controls and switches for heat, air, ventilation, etc. We also pressurize a/c systems with DRY air and use soap solution to find leaks there. A little soapy water spray doesn't seem to hurt a carpet or anything under the dash. -
