Have a 1968 302 J code, edlebrock intake, mild Hyd Flat tap cam, headers. 600 Holley, stock compression. One plug #6 suggest cylinder is running lean (very white plug porcelain and spark mark on plug porcelaine vary faint. However all other 7 cylinders are burning well, slightly brown. Would think it might be a timing, jetting issue, or plug heat range except it is only on one cylinder. Compression check on cylinders revealed about 160 Lbs-(dry) to include #6. Took off and reinstalled intake, thought might have an internal vacumm leak to #6. All pushrods are straight Strong and steady vacuum on engine when running. Good spark at #6 plug. The only think I can think of is cam issue for intake value on #6 or lifter is collapsing during intake cycle. Any comments or suggestions would be appreciated.