Thanks for the info guys, mine has a pronounced lope over other 400's that I have heard run and I imagine the RA1's are even more so.
I would think that the 224/336 would provide a little more low end torque than the 212/225. (Not that any Pontiac lacks torque)
Duration is the amount of time in crankshaft degrees that the valve is off the seat (open). Generally the power band moves up the rpm curve as the duration gets larger, and you lose low end.
