which 3'' exhaust do i want?

It's not a theory it is fact that to large an exhaust system can lower torgue and HP except in a forced induction setup, then there is no such thing as too large an exhaust system. A N/A motor uses heat and exhaust tubing size to help scavange the cylinders. For example I am using 2" primary tube headers on my Valiant and I know I am loosing some low rpm torgue and should use a smaller tube header because they are too large but I got a great deal on then so I used them. They would be fine if my car was lighter or had more gear but never the less with the package I have they are two large.

Your example about the Firechicken means nothing, that was a complete different package than you are talking about now and different packages respond differently with different changes. Your Dart may actually run better with a bigger exhaust system but just because it is bigger doesn't automatically mean it will run better. I have a buddy with a '70 Chevelle 396 and he used to run it uncorked. After some test and tune sessions it turned out that the car would ET better with the exhaust corked. It would 60' better which translated in a quicker ET. His MPH did not change which meant he really didn't loose any HP but did gain torque because it ran a better ET. I not saying don't put on the larger exhaust I am saying it is very possible that you can receive no gain in power and can actually loose power depending on the package you have.


Chuck