A muffler for an internal combustion engine includes a first shell includes a flexible portion, an intake conduit, and a second shell coupled to the first shell. The intake conduit extends outwardly from the first shell and is configured to be inserted into an exhaust port of an engine. The flexible portion surrounds the intake conduit. Upon attachment to the engine, compression force is stored via elastic deflection of the flexible portion of the first shell, thereby pressing the intake conduit into the exhaust port such that a seal is formed.