This is a long shot but does anybody have experience with a lifter making a racket? The leak down checks out fine. I changed all the lifters and pulled the head and had it checked... twice! Nothing appears to be wrong. The camshaft is perfect, lifters all feel OK, the valve stem heights are all in spec. I even swapped cam shaft housings. Yet, there is one lifter, somewhere in the middile of the motor, clacking away.

I went to the dyno shop (for a different issue) and ran the car, and after 3 runs there is still some lifter noise. The guys at the dyno shop commented on it so it's not my over-sensitive ear. It's really noisy at start-up and gets better as the motor warms up.

Any ideas most welcome. I've bailed on 3 races this year already - I want to resolve this first.

TIA
Tim