Freshly rebuilt, forged pistons, Comp cams, runs great. The only thing is, this '97 4.6L makes this irritating and LOUD chattering noise when I get off the gas. I've mentioned it here before, but I've always thought it was related to the supercharger. We took the serpentine belt off, which isolated all the external stuff including the Allen SC. It still made the noise. Besides being irritating, I get nervous something is gonna break.

Any ideas? Could it be in the valve train? Related to the cam installation maybe?

 

chain tensioners, guide worn
crank sensor ring installed wrong
torque converter bolts to flex plate not tight, or installed wrong
just a few possibles....