Originally Posted by TrueStreetTim
Both headers on a N/A setup will make similar peak HP. Difference is; the smaller header diameter will make torque, and more of it, sooner and more than likely more peak torque.
Headers are efficient until they become a restriction. In the case of a N/A, 302ci motor a 1-7/8 header is overkill and can therefore benefit with the increase in torque you find in a smaller design. A 370ci motor (LS3 etc) or a boosted 302.... 1-7/8 all day.
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as the smaller diameter will make more tq, how much more are we talking about? I'm just shooting for 420-425ish hp and as close to possible tq to that horsepower. In a perfect world i'd like 420-425hp and 395-405tq