440 power gains/ aluminum head advantages?

yeah for a new set from what i've read it's a bit loose. people say 1/2 deflection is the point of replacement. that can't be the total loss of power though because it is probably only a couple degrees of movement. hoping the timing kit is out of degree. after work today i'll pull the intake and plugs and check the cam. answers will be given soon!
Make double sure you get top dead center on piston or any numbers you come up with are wrong