Porter Mufflers They are back! The famous heavy-duty mufflers that were used by the original hot-rodders in the 1940s and '50s are available once again. For those who are not familiar with Porter Mufflers, they are vintage steel-pac mufflers that have a very deep, desirable, unique sound. Porter Mufflers are still hand manufactured right here in the U.S.A. just like they were back in the 1930s.