By looking at the dizzy it looks as if the clearence was not set right with the brass gear. Did you measure it after installing the gear. I am not quite sure on the 400's but on the 302's and 351's require a distance of 3.996 to 4.005 from face of gear to face of dizzy.

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1992 mustang lx coupe, caged, mini tubbed, 393 with Novi2k supercharger 11lbs of boost, BS3 EFI on 93 octane. 9.47 @144
1997 F350 psd 4x4 http://media.putfile.com/Mustang-Novi2k