i had the same noise in my car and it came and went then the motor just went it is way 2 fast 2 be a lifter and even if so.. noises travle travle throught the motor do you have a after marked boost gauge and dose the car miss fire at all..? that would let you know if it is in the valve train .. that is a hard noise that dunt sound soft trust me i ave done many 3800 motors i am doing one now in my car now because of the same type noise ...