Well, after 9 months of waiting, my new 455 was in the Trans Am, and ready for it's first test drive.
The beast roared to life, and shook the ground with the mighty rumpity-rump of a healthy cam and valve train.
The torque was unbeleivable! Despite the tender way I was working the gas pedal and Centerforce clutch, 500+ ft/lbs of torque was making it a chore not to bark the tires at every green light.
But a persistant knock was coming from the engine. A cold sweat washed over me as I considered the worst of two possibilities...either I have a bad lifter, or my cam is slowly being machined to a nice round candlestick shape.
I limp on over to the performance shop that built my motor (
BTW, he's the best performance buider in town...but a mostly CHEVY builder, as no one around knows Pontiacs 
My first red flag was when he advised me that putting a 455 Pontiac motor in my TA might require modifying the hood, because the motor was too tall 
... I quickly realized he was actually talking about a 455 OLDS motor 
).
Anyway, the builder is adament that ANOTHER shop (the one who installed the motor, and did the 20-min. break-in), must be at fault. I spend a full day trying to get the straight story from the buidler, the installer, and Comp Cams.
To make a long story short, it turns out the builder didn't "soft-spring" the valve-train for the initial break-in (that is, using single springs)...his "explanation" was that you usually don't soft-spring unless you're building a racing motor.
Yet, Comp Cams' instructions clearly state you have to soft-spring the motor until the cam is broken in. I wonder how many builders don't read the instructions, and blame thier flat cams on poor product?
Just a thought.