How big of a header works on SBC ?

[hoffman900]

Almost every header for the 604ci Crate Engines are 1 5/8" off the head, and could really be 1 1/2".

[Frankshaft]

The answer is simply, its application specific. Run an f2r with 30 lbs of boost, or run a 440 sbc that makes 900 on motor, and then spray it with another 600, gaurentee you aren't running a 1 7/8 for max power. Restricted engines have nothing to get rid of, and don't make any power, that's why the small header is better. Simply un restric it, put a good 4 barrel intake and carb, and change the cam in that same engine, and watch it want a bigger header. The simple, but complicated answer is that its application specific.