[Boog]

That sounds an awful lot like the lifter issue the early 454's had. After warm up lifter clack appeared and this was with a stock engine. Oil pressure was good but it clacked after warm up. Usually it was on cylinder #1. The GM fix was to drill a small hole in the lifter galley plug at the front of the block next to #1 cylinder to let the hot oil out and fresh oil into the lifters. Dad and I drilled his to cure his lifter clack after having replaced those lifters several times. No more problems. There was a service bulletin back then so this information came from GM in the early 70's.