There's definetly more to it than recurving and rejetting. To get these times, these engines are balanced and blueprinted, something that is rarely done at the factory. They are allowed a boost in compression and these builders are also aided by the use of a dyno to supertune their engines. As Jody has posted earlier, the 2 1/2" mandrel bent exhaust system with an X pipe flows much better than the old 2 1/4' factory bent system. Just take a look at a '71-'72 Trans Am with stock 455 HO 2 1/4" head pipes as they come out of the exhaust manifolds. The first 90 degree bend is crushed down to probably 1 7/8", and as you follow the system back, there are similar bends going into the single crossflow muffler. This has always been a horsepower-robbing system.
I'm sure everyone has their own little tricks, but with such a large number of cars turning 12's, are we to assume that everyone is cheating? We are seeing RA II's, RA IV's, 455 HO's, and SD 455's getting into the mid-12's, not to mention all the others makes that are turning these times. I say give these guys credit for a job well done.
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