The easiest way is get a rag & stuff it on the side of the site plugs, then take them out & adjust, on a 4160 with the metering plate it helps if you adj. the rear a bit higher then the front.

75 Duster, 451 10.87 @ 123.58 NA 97 Z28 6sp., 12.01 @ 115 on a 100 shot 71 Swinger. 360 magnum. 12.58 @ 105 78 cutlass, 469 BBC. 12.70 @ 108 on street tires. http://www.youtube.com/watch?v=Z2kqNmMfheU