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The Flowmaster Original 40 Series is one of the company’s most recognizable performance muffler families and is aimed at drivers who want the classic, aggressive Flowmaster sound. The series is designed for street/strip, off-road, muscle-car, truck, and custom exhaust applications where exterior tone is a major part of the build. Flowmaster characterizes the Original 40 Series with an aggressive exterior exhaust note and noticeable interior resonance, so it is a better match for enthusiasts who want to hear the exhaust inside the vehicle rather than those seeking near-stock refinement. The fully welded construction is built for durability, with versions offered in aluminized steel and 409 stainless steel depending on the part number. The design does not rely on traditional sound-absorbing packing material, helping the muffler maintain its sound character over time. Multiple inlet and outlet layouts make the Original 40 Series useful for a wide variety of custom exhaust configurations, including center, offset, dual-inlet, and dual-outlet arrangements. Its compact oval body also gives fabricators a familiar footprint that works well in many universal installations. If the goal is a traditional Flowmaster tone with a strong presence at idle and under acceleration, the Original 40 Series remains a straightforward choice for performance street cars, classic muscle, pickups, and off-road builds.
