I've heard that forged pistons will make noise in a Cleveland until they're warmed up and expanded. Because of that, when I rebuilt my Cleveland years ago I went with Keith Black Hypereutectic pistons (they are silicon impregnated cast pistons). My motor was about 450hp, and I never had a problem with it. I drove it hard for years.
Here's more info on the subject:
http://en.wikipedia.org/wiki/Hypereutectic_piston
Michael
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