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Old 12-18-2009, 09:42 PM
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Hankrod Hankrod is offline
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Join Date: Jun 22, 2005
Location: Fond du Lac, WI
Posts: 272
Pull the plug wires one at a time with it running and see if it has any effect. Or you can just short the wires one at a time to the battery positive terminal and that will prevent the plug from firing. You have something interrupting the steady vacuum signal. Either a bad valve or a out of place combustion activity. To make a vac. gauge move that much, a reversion must be occurring. Are the pushrods the correct length? Did you check the lifter preload when the rockers where installed? do you have adjustable rockers? The heads or block may not be straight and allowing just one of the outer valves/pushrods to run a little tight, and this may not show up in a compression test. Just trying to help. Good luck, Hankrod
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