No, they are not. Heads hold the key to most of the power potential of the engine (along with cam selection). A stock iron head flows ~190cfm...a stock Edelbrock head flows ~ 250cfm, Fully ported Edelbrocks flow ~ 293cfm (at least mine do), Indy heads (fully ported) can go north of 320cfm, etc. Those are big differences in power potential (~375hp-650hp). In order to take advantage of that head flow you need a cam that can operate in the range to maximize flow....What Rumble was saying in his response is true, you need to look at the whole package and make a plan. Start with a goal (an ET, HP number, etc.) and build from there. Obviously there are many critical components, but good flowing heads are essential to making big power.
