2" to 3" exhaust... Worth it?

rumblefish360 said

The best way to get the most torque is with the same size exhaust pipe as the collector for a certain amount of inches, which varies. Engine masters did a thing in that. I don’t want to blanket statement “Use an 18” length of pipe…” At the pipes end, you need a pressure cancellation box or at least as many square inches as the engine is. Then continue with the exhaust pipe into the muffler.

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From David Vizard's "How to Build Horsepower", cross-plane V8s (like we deal with) are much more sensitive to secondary tuning length than primary. According to the book even adding just 12" to the collector length gave a boost of 40 ft-lbs and 12 hp on a ~370 hp engine. David says, "On occasion I have built V-8 exhaust systems for street use with a secondary as long as 60 inches. This proved to be capable of boosting low-speed (2,000 to 3,000 rpm) torque as much as 20 ft-lbs over a more usual 20- to 30-inch collector."

Makes sense you see that "equal-length headers" are much more commonly available for 4- and 6-cylinder engines since primary tuning has more of an effect on those configurations than secondary tuning. Equal-length primaries on a V-8 don't really do anything, it's everything downstream of where the primaries merge that matters.