because the charger has MDS. and he probably swapped out the lifters to remove it. (lifters are under the head) or to swap out the valve springs. as they must be changed for just about all cam swaps. it can be done with the head on the motor, but without the correct spring compressor tool its just about impossable. i pull them every time because i dont want to worry about loosing a valve spring keeper, or dropping a valve into the motor. to me its just easier.
